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98-443: The subimages are then stored in the image file in numerical order. Adam7 uses seven passes and operates in both dimensions, compared to only four passes in the vertical dimension used by GIF . This means that an approximation of the entire image can be perceived much more quickly in the early passes, particularly if interpolation algorithms such as bicubic interpolation are used. Adam7 is named after Adam M. Costello, who suggested

196-567: A > . Such a collection of useful, related resources, interconnected via hypertext links is dubbed a web of information. Publication on the Internet created what Tim Berners-Lee first called the WorldWideWeb (in its original CamelCase , which was subsequently discarded) in November 1990. The hyperlink structure of the web is described by the webgraph : the nodes of the web graph correspond to

294-520: A home page containing a directory of the site web content . Some websites require user registration or subscription to access content. Examples of subscription websites include many business sites, news websites, academic journal websites, gaming websites, file-sharing websites, message boards , web-based email , social networking websites, websites providing real-time price quotations for different types of markets, as well as sites providing various other services. End users can access websites on

392-494: A web application . Consequently, a static web page displays the same information for all users, from all contexts, subject to modern capabilities of a web server to negotiate content-type or language of the document where such versions are available and the server is configured to do so. A server-side dynamic web page is a web page whose construction is controlled by an application server processing server-side scripts. In server-side scripting, parameters determine how

490-578: A web page on the World Wide Web normally begins either by typing the URL of the page into a web browser or by following a hyperlink to that page or resource. The web browser then initiates a series of background communication messages to fetch and display the requested page. In the 1990s, using a browser to view web pages—and to move from one web page to another through hyperlinks—came to be known as 'browsing,' 'web surfing' (after channel surfing ), or 'navigating

588-399: A 9-pass scheme, an 11-pass scheme, and so forth, or alternatively an adaptive number of passes can be used, as many as the image size will allow (so the first pass consists of a single pixel), as is usual in scale-free multiscale modeling. In the context that PNG was developed (i.e., for the image sizes and connection speeds in question), a 7-pass scheme was seen as sufficient, and preferable to

686-448: A GIF file describes a fixed-sized graphical area (the "logical screen") populated with zero or more "images". Many GIF files have a single image that fills the entire logical screen. Others divide the logical screen into separate sub-images. The images may also function as animation frames in an animated GIF file, but again these need not fill the entire logical screen. GIF files start with a fixed-length header ("GIF87a" or "GIF89a") giving

784-537: A browser called WorldWideWeb (which became the name of the project and of the network) and an HTTP server running at CERN. As part of that development he defined the first version of the HTTP protocol, the basic URL syntax, and implicitly made HTML the primary document format. The technology was released outside CERN to other research institutions starting in January 1991, and then to the whole Internet on 23 August 1991. The Web

882-611: A frenzy for the Web and started the dot-com bubble . Microsoft responded by developing its own browser, Internet Explorer , starting the browser wars . By bundling it with Windows, it became the dominant browser for 14 years. Berners-Lee founded the World Wide Web Consortium (W3C) which created XML in 1996 and recommended replacing HTML with stricter XHTML . In the meantime, developers began exploiting an IE feature called XMLHttpRequest to make Ajax applications and launched

980-506: A limited number of colors, such as logos. This takes advantage of the format's lossless compression, which favors flat areas of uniform color with well defined edges. They can also be used to store low-color sprite data for games. GIFs can be used for small animations and low-resolution video clips, or as reactions in online messaging used to convey emotion and feelings instead of using words. They are popular on social media platforms such as Tumblr , Facebook and Twitter . Conceptually,

1078-479: A network, a web browser can retrieve a web page from a remote web server . The web server may restrict access to a private network such as a corporate intranet. The web browser uses the Hypertext Transfer Protocol (HTTP) to make such requests to the web server . A static web page is delivered exactly as stored, as web content in the web server's file system . In contrast, a dynamic web page

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1176-465: A partially downloaded image was somewhat recognizable, also helped GIF's popularity, as a user could abort the download if it was not what was required. In May 2015 Facebook added support for GIF. In January 2018 Instagram also added GIF stickers to the story mode. In 2016 the Internet Archive released a searchable library of GIFs from their Geocities archive. As a noun , the word GIF

1274-627: A particular topic or purpose, ranging from entertainment and social networking to providing news and education. All publicly accessible websites collectively constitute the World Wide Web, while private websites, such as a company's website for its employees, are typically a part of an intranet . Web pages, which are the building blocks of websites, are documents , typically composed in plain text interspersed with formatting instructions of Hypertext Markup Language ( HTML , XHTML ). They may incorporate elements from other websites with suitable markup anchors . Web pages are accessed and transported with

1372-467: A public Internet Protocol (IP) network, such as the Internet , or a private local area network (LAN), by referencing a uniform resource locator (URL) that identifies the site. Websites can have many functions and can be used in various fashions; a website can be a personal website , a corporate website for a company, a government website, an organization website, etc. Websites are typically dedicated to

1470-422: A range of devices, including desktop and laptop computers , tablet computers , smartphones and smart TVs . A web browser (commonly referred to as a browser ) is a software user agent for accessing information on the World Wide Web. To connect to a website's server and display its pages, a user needs to have a web browser program. This is the program that the user runs to download, format, and display

1568-415: A search of the table for each pixel. A linear search through up to 4096 addresses would make the coding slow. In practice the codes can be stored in order of numerical value; this allows each search to be done by a SAR (Successive Approximation Register, as used in some ADCs ), with only 12 magnitude comparisons. For this efficiency an extra table is needed to convert between codes and actual memory addresses;

1666-427: A simple 5-pass scheme. GIF The Graphics Interchange Format ( GIF ; / ɡ ɪ f / GHIF or / dʒ ɪ f / JIF , see § Pronunciation ) is a bitmap image format that was developed by a team at the online services provider CompuServe led by American computer scientist Steve Wilhite and released on June 15, 1987. The format can contain up to 8 bits per pixel , allowing

1764-515: A single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space . It can also represent multiple images in a file, which can be used for animations , and allows a separate palette of up to 256 colors for each frame. These palette limitations make GIF less suitable for reproducing color photographs and other images with color gradients but well-suited for simpler images such as graphics or logos with solid areas of color. GIF images are compressed using

1862-439: A translation that reflects the design concept and proliferation of the World Wide Web. Use of the www prefix has been declining, especially when web applications sought to brand their domain names and make them easily pronounceable. As the mobile Web grew in popularity, services like Gmail .com, Outlook.com , Myspace .com, Facebook .com and Twitter .com are most often mentioned without adding "www." (or, indeed, ".com") to

1960-429: A web browser in its address bar input field, some web browsers automatically try adding the prefix "www" to the beginning of it and possibly ".com", ".org" and ".net" at the end, depending on what might be missing. For example, entering "microsoft" may be transformed to http://www.microsoft.com/ and "openoffice" to http://www.openoffice.org . This feature started appearing in early versions of Firefox , when it still had

2058-429: A web page on the user's computer. In addition to allowing users to find, display, and move between web pages, a web browser will usually have features like keeping bookmarks, recording history, managing cookies (see below), and home pages and may have facilities for recording passwords for logging into web sites. The most popular browsers are Chrome , Firefox , Safari , Internet Explorer , and Edge . A Web server

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2156-498: A year. Mosaic was a graphical browser that could display inline images and submit forms that were processed by the HTTPd server . Marc Andreessen and Jim Clark founded Netscape the following year and released the Navigator browser , which introduced Java and JavaScript to the Web. It quickly became the dominant browser. Netscape became a public company in 1995 which triggered

2254-448: Is 2, even if only values 0 and 1 are used. The code table initially contains codes that are one bit longer than the symbol size in order to accommodate the two special codes clr and end and codes for strings that are added during the process. When the table is full the code length increases to give space for more strings, up to a maximum code 4095 = FFF(hex). As the decoder builds its table it tracks these increases in code length and it

2352-532: Is able to unpack incoming bytes accordingly. A 46×46 uncompressed GIF with 7-bit symbols (128 colors, 8-bit codes). Click on the image for an explanation of the code. World Wide Web The World Wide Web ( WWW or simply the Web ) is an information system that enables content sharing over the Internet through user-friendly ways meant to appeal to users beyond IT specialists and hobbyists. It allows documents and other web resources to be accessed over

2450-522: Is almost never used for true color images, it is possible to do so. A GIF image can include multiple image blocks, each of which can have its own 256-color palette, and the blocks can be tiled to create a complete image. Alternatively, the GIF89a specification introduced the idea of a "transparent" color where each image block can include its own palette of 255 visible colors plus one transparent color. A complete image can be created by layering image blocks with

2548-441: Is delivered with the page that can make additional HTTP requests to the server, either in response to user actions such as mouse movements or clicks, or based on elapsed time. The server's responses are used to modify the current page rather than creating a new page with each response, so the server needs only to provide limited, incremental information. Multiple Ajax requests can be handled at the same time, and users can interact with

2646-632: Is found in the newer editions of many dictionaries. In 2012, the American wing of the Oxford University Press recognized GIF as a verb as well, meaning "to create a GIF file", as in "GIFing was the perfect medium for sharing scenes from the Summer Olympics ". The press's lexicographers voted it their word of the year , saying that GIFs have evolved into "a tool with serious applications including research and journalism". The pronunciation of

2744-403: Is generated by a web application , usually driven by server-side software . Dynamic web pages are used when each user may require completely different information, for example, bank websites, web email etc. A static web page (sometimes called a flat page/stationary page ) is a web page that is delivered to the user exactly as stored, in contrast to dynamic web pages which are generated by

2842-446: Is not required by any technical or policy standard and many websites do not use it; the first web server was nxoc01.cern.ch . According to Paolo Palazzi, who worked at CERN along with Tim Berners-Lee, the popular use of www as subdomain was accidental; the World Wide Web project page was intended to be published at www.cern.ch while info.cern.ch was intended to be the CERN home page; however

2940-459: Is officially spelled as three separate words, each capitalised, with no intervening hyphens. Nonetheless, it is often called simply the Web , and also often the web ; see Capitalization of Internet for details. In Mandarin Chinese, World Wide Web is commonly translated via a phono-semantic matching to wàn wéi wǎng ( 万维网 ), which satisfies www and literally means "10,000-dimensional net",

3038-476: Is prefixed with a byte indicating the number of data bytes in the sub-block. The series of sub-blocks is terminated by an empty sub-block (a single 0 byte, indicating a sub-block with 0 data bytes). For the sample image above the reversible mapping between 9-bit codes and bytes is shown below. A slight compression is evident: pixel colors defined initially by 15 bytes are exactly represented by 12 code bytes including control codes. The encoding process that produces

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3136-527: Is the best known of such efforts. Many hostnames used for the World Wide Web begin with www because of the long-standing practice of naming Internet hosts according to the services they provide. The hostname of a web server is often www , in the same way that it may be ftp for an FTP server , and news or nntp for a Usenet news server . These hostnames appear as Domain Name System (DNS) or subdomain names, as in www.example.com . The use of www

3234-407: Is the common practice of following such hyperlinks across multiple websites. Web applications are web pages that function as application software . The information in the Web is transferred across the Internet using HTTP. Multiple web resources with a common theme and usually a common domain name make up a website . A single web server may provide multiple websites, while some websites, especially

3332-435: Is the standard markup language for creating web pages and web applications . With Cascading Style Sheets (CSS) and JavaScript , it forms a triad of cornerstone technologies for the World Wide Web. Web browsers receive HTML documents from a web server or from local storage and render the documents into multimedia web pages. HTML describes the structure of a web page semantically and originally included cues for

3430-431: The Hypertext Transfer Protocol (HTTP), which may optionally employ encryption ( HTTP Secure , HTTPS) to provide security and privacy for the user. The user's application, often a web browser , renders the page content according to its HTML markup instructions onto a display terminal . Hyperlinking between web pages conveys to the reader the site structure and guides the navigation of the site, which often starts with

3528-661: The Lempel–Ziv–Welch (LZW) lossless data compression technique to reduce the file size without degrading the visual quality. While once in widespread usage on the World Wide Web because of its wide implementation and portability between applications and operating systems, usage of the format has declined for space and quality reasons, often being replaced with video formats such as the MP4 file format . These replacements, in turn, are sometimes termed "GIFs" despite having no relation to

3626-694: The Web 2.0 revolution. Mozilla , Opera , and Apple rejected XHTML and created the WHATWG which developed HTML5 . In 2009, the W3C conceded and abandoned XHTML. In 2019, it ceded control of the HTML specification to the WHATWG. The World Wide Web has been central to the development of the Information Age and is the primary tool billions of people use to interact on the Internet . Tim Berners-Lee states that World Wide Web

3724-578: The web browsing history forward of the displayed page. Using Ajax technologies the end user gets one dynamic page managed as a single page in the web browser while the actual web content rendered on that page can vary. The Ajax engine sits only on the browser requesting parts of its DOM, the DOM, for its client, from an application server. Dynamic HTML, or DHTML, is the umbrella term for technologies and methods used to create web pages that are not static web pages , though it has fallen out of common use since

3822-422: The 9-bit codes is shown below. A local string accumulates pixel color numbers from the palette, with no output action as long as the local string can be found in a code table. There is special treatment of the first two pixels that arrive before the table grows from its initial size by additions of strings. After each output code, the local string is initialized to the latest pixel color (that could not be included in

3920-470: The DNS records were never switched, and the practice of prepending www to an institution's website domain name was subsequently copied. Many established websites still use the prefix, or they employ other subdomain names such as www2 , secure or en for special purposes. Many such web servers are set up so that both the main domain name (e.g., example.com) and the www subdomain (e.g., www.example.com) refer to

4018-542: The GIF specification, dithering can be used in images subsequently encoded as GIF images. This is often not an ideal solution for GIF images, both because the loss of spatial resolution typically makes an image look fuzzy on the screen, and because the dithering patterns often interfere with the compressibility of the image data, working against GIF's main purpose. In the early days of graphical web browsers , graphics cards with 8-bit buffers (allowing only 256 colors) were common and it

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4116-410: The GIF specification. GIF is palette-based: the colors used in an image (a frame) in the file have their RGB values defined in a palette table that can hold up to 256 entries, and the data for the image refer to the colors by their indices (0–255) in the palette table. The color definitions in the palette can be drawn from a color space of millions of shades (2 shades, 8 bits for each primary), but

4214-452: The HTML and the CSS standards, has encouraged the use of CSS over explicit presentational HTML since 1997. Most web pages contain hyperlinks to other related pages and perhaps to downloadable files, source documents, definitions and other web resources. In the underlying HTML, a hyperlink looks like this: < a href = "http://example.org/home.html" > Example.org Homepage </

4312-423: The HTTP service so that the receiving host can distinguish an HTTP request from other network protocols it may be servicing. HTTP normally uses port number 80 and for HTTPS it normally uses port number 443 . The content of the HTTP request can be as simple as two lines of text: The computer receiving the HTTP request delivers it to web server software listening for requests on port 80. If the web server can fulfil

4410-449: The Internet according to specific rules of the Hypertext Transfer Protocol (HTTP). The Web was invented by English computer scientist Tim Berners-Lee while at CERN in 1989 and opened to the public in 1991. It was conceived as a "universal linked information system". Documents and other media content are made available to the network through web servers and can be accessed by programs such as web browsers . Servers and resources on

4508-411: The Internet. The Web was invented by English computer scientist Tim Berners-Lee while working at CERN . He was motivated by the problem of storing, updating, and finding documents and data files in that large and constantly changing organization, as well as distributing them to collaborators outside CERN. In his design, Berners-Lee dismissed the common tree structure approach, used for instance in

4606-508: The URLs of other resources such as images, other embedded media, scripts that affect page behaviour, and Cascading Style Sheets that affect page layout. The browser makes additional HTTP requests to the web server for these other Internet media types . As it receives their content from the web server, the browser progressively renders the page onto the screen as specified by its HTML and these additional resources. Hypertext Markup Language (HTML)

4704-448: The Web'. Early studies of this new behaviour investigated user patterns in using web browsers. One study, for example, found five user patterns: exploratory surfing, window surfing, evolved surfing, bounded navigation and targeted navigation. The following example demonstrates the functioning of a web browser when accessing a page at the URL http://example.org/home.html . The browser resolves

4802-671: The World Wide Web and web browsers . A web browser displays a web page on a monitor or mobile device . The term web page usually refers to what is visible, but may also refer to the contents of the computer file itself, which is usually a text file containing hypertext written in HTML or a comparable markup language . Typical web pages provide hypertext for browsing to other web pages via hyperlinks , often referred to as links . Web browsers will frequently have to access multiple web resource elements, such as reading style sheets , scripts , and images, while presenting each web page. On

4900-612: The World Wide Web are identified and located through character strings called uniform resource locators (URLs). The original and still very common document type is a web page formatted in Hypertext Markup Language (HTML). This markup language supports plain text , images , embedded video and audio contents, and scripts (short programs) that implement complex user interaction. The HTML language also supports hyperlinks (embedded URLs) which provide immediate access to other web resources. Web navigation , or web surfing,

4998-543: The appearance of the document. HTML elements are the building blocks of HTML pages. With HTML constructs, images and other objects such as interactive forms may be embedded into the rendered page. HTML provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links , quotes and other items. HTML elements are delineated by tags , written using angle brackets . Tags such as < img /> and < input /> directly introduce content into

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5096-449: The assembly of every new web page proceeds, including the setting up of more client-side processing. A client-side dynamic web page processes the web page using JavaScript running in the browser. JavaScript programs can interact with the document via Document Object Model , or DOM, to query page state and alter it. The same client-side techniques can then dynamically update or change the DOM in

5194-443: The color of the pixel in the same position from the background, which may have been determined by a previous frame of animation. Many techniques, collectively called dithering , have been developed to approximate a wider range of colors with a small color palette by using pixels of two or more colors to approximate in-between colors. These techniques sacrifice spatial resolution to approximate deeper color resolution. While not part of

5292-427: The complete, full-color image appears. For example, breaking an image into tiles of 16 by 16 pixels (256 pixels in total) ensures that no tile has more than the local palette limit of 256 colors, although larger tiles may be used and similar colors merged resulting in some loss of color information. Since each image block can have its own local color table, a GIF file having many image blocks can be very large, limiting

5390-472: The development of the Portable Network Graphics (PNG) standard. In 2004, all patents relating to the proprietary compression used for GIF expired. The feature of storing multiple images in one file, accompanied by control data, is used extensively on the Web to produce simple animations . The optional interlacing feature, which stores image scan lines out of order in such a fashion that even

5488-656: The domain. In English, www is usually read as double-u double-u double-u . Some users pronounce it dub-dub-dub , particularly in New Zealand. Stephen Fry , in his "Podgrams" series of podcasts, pronounces it wuh wuh wuh . The English writer Douglas Adams once quipped in The Independent on Sunday (1999): "The World Wide Web is the only thing I know of whose shortened form takes three times longer to say than what it's short for". The terms Internet and World Wide Web are often used without much distinction. However,

5586-408: The early stages, in return for simpler implementation. Adam7 arises from iteration of the following pattern: which may be interpreted as "folding" in the vertical and horizontal dimensions. Similarly, GIF interlacing 1324 can be seen as iteration of the 12 pattern, but only in the vertical direction ( 12 expands to 1.2. which is filled in as 1324 ). Using this 3-pass pattern means

5684-457: The example. If the palette is only 64 colors (so color indexes are 6 bits wide), the symbols can range from 0 to 63, and the symbol width can be taken to be 6 bits, with codes starting at 7 bits. In fact, the symbol width need not match the palette size: as long as the values decoded are always less than the number of colors in the palette, the symbols can be any width from 2 to 8, and the palette size any power of 2 from 2 to 256. For example, if only

5782-555: The existing CERNDOC documentation system and in the Unix filesystem , as well as approaches that relied in tagging files with keywords , as in the VAX/NOTES system. Instead he adopted concepts he had put into practice with his private ENQUIRE system (1980) built at CERN. When he became aware of Ted Nelson 's hypertext model (1965), in which documents can be linked in unconstrained ways through hyperlinks associated with "hot spots" embedded in

5880-408: The extra table upkeeping is needed only when a new code is stored which happens at much less than pixel rate. Decoding begins by mapping the stored bytes back to 9-bit codes. These are decoded to recover the pixel colors as shown below. A table identical to the one used in the encoder is built by adding strings by this rule: Shorter code lengths can be used for palettes smaller than the 256 colors in

5978-414: The first code is stored in the least significant bit of the first byte, higher order bits of the code into higher order bits of the byte, spilling over into the low order bits of the next byte as necessary. Each subsequent code is stored starting at the least significant bit not already used. This byte stream is stored in the file as a series of "sub-blocks". Each sub-block has a maximum length 255 bytes and

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6076-419: The first four colors (values 0 to 3) of the palette are used, the symbols can be taken to be 2 bits wide with codes starting at 3 bits. Conversely, the symbol width could be set at 8, even if only values 0 and 1 are used; these data would only require a two-color table. Although there would be no point in encoding the file that way, something similar typically happens for bi-color images: the minimum symbol width

6174-487: The first letter of GIF has been disputed since the 1990s. The most common pronunciations in English are / dʒ ɪ f / (with a soft g as in gin ) and / ɡ ɪ f / (with a hard g as in gift ), differing in the phoneme represented by the letter G . The creators of the format pronounced the acronym GIF as / dʒ ɪ f / , with a soft g , with Wilhite stating that he intended for

6272-419: The first pass is (1/2) = 1/4 (25%) of the image. Iterating this pattern once yields a 5-pass scheme; after 3 passes this yields which is then filled in to: In the 5-pass pattern, the first pass (1/4) = 1/16 (6.25%) of the image. Iterating again yields the 7-pass Adam7 scheme, where the first pass (1/8) = 1/64 (1.5625%) of the image. In principle this can be iterated, yielding

6370-413: The following tables are in little-endian byte order, as the format specification prescribes. The image pixel data, scanned horizontally from top left, are converted by LZW encoding to codes that are then mapped into bytes for storing in the file. The pixel codes typically don't match the 8-bit size of the bytes, so the codes are packed into bytes by a "little-Endian" scheme: the least significant bit of

6468-422: The image will generally be interpolated at earlier stages, rather than just these pixels being rendered. Adam7 is a multiscale model of the data, similar to a discrete wavelet transform with Haar wavelets , though it starts from an 8×8 block, and downsamples the image, rather than decimating ( low-pass filtering , then downsampling). It thus offers worse frequency behavior, showing artifacts ( pixelation ) at

6566-408: The maximum number of colors a frame can use is 256. This limitation was reasonable when GIF was developed because hardware that could display more than 256 colors simultaneously was rare. Simple graphics, line drawings, cartoons, and grey-scale photographs typically need fewer than 256 colors. Each frame can designate one index as a "transparent background color": any pixel assigned this index takes on

6664-444: The method on February 2, 1995, and after the seven steps involved. It is a rearrangement of this five-pass scheme that had earlier been proposed by Lee Daniel Crocker : Alternative speculative proposals at the time included square spiral interlacing and using Peano curves , but these were rejected as being overcomplicated. The pixels included in each pass, and the total pixels encoded at that point are as follows: When rendering,

6762-433: The most popular ones, may be provided by multiple servers. Website content is provided by a myriad of companies, organizations, government agencies, and individual users ; and comprises an enormous amount of educational, entertainment, commercial, and government information. The Web has become the world's dominant information systems platform . It is the primary tool that billions of people worldwide use to interact with

6860-503: The new system to documents organized in other ways (such as traditional computer file systems or the Usenet ). Finally, he insisted that the system should be decentralized, without any central control or coordination over the creation of links. Berners-Lee submitted a proposal to CERN in May 1989, without giving the system a name. He got a working system implemented by the end of 1990, including

6958-505: The original file format. CompuServe introduced GIF on 15 June 1987 to provide a color image format for their file downloading areas. This replaced their earlier run-length encoding format, which was black and white only. GIF became popular because it used Lempel–Ziv–Welch data compression . Since this was more efficient than the run-length encoding used by PCX and MacPaint , fairly large images could be downloaded reasonably quickly even with slow modems . The original version of GIF

7056-456: The output code). For clarity the table is shown above as being built of strings of increasing length. That scheme can function but the table consumes an unpredictable amount of memory. Memory can be saved in practice by noting that each new string to be stored consists of a previously stored string augmented by one character. It is economical to store at each address only two words: an existing address and one character. The LZW algorithm requires

7154-466: The owners of the Jif brand, partnered with the animated image database and search engine Giphy to release a limited-edition "Jif vs. GIF" ( hashtagged as #JIFvsGIF) jar of peanut butter that had a label humorously declaring the soft- g pronunciation to refer exclusively to the peanut butter, and GIF to be exclusively pronounced with the hard- g pronunciation. GIFs are suitable for sharp-edged line art with

7252-427: The page while data is retrieved. Web pages may also regularly poll the server to check whether new information is available. A website is a collection of related web resources including web pages , multimedia content, typically identified with a common domain name , and published on at least one web server . Notable examples are wikipedia .org, google .com, and amazon.com . A website may be accessible via

7350-485: The page. Other tags such as < p > surround and provide information about document text and may include other tags as sub-elements. Browsers do not display the HTML tags, but use them to interpret the content of the page. HTML can embed programs written in a scripting language such as JavaScript , which affects the behaviour and content of web pages. Inclusion of CSS defines the look and layout of content. The World Wide Web Consortium (W3C), maintainer of both

7448-542: The popularization of AJAX , a term which is now itself rarely used. Client-side-scripting, server-side scripting, or a combination of these make for the dynamic web experience in a browser. JavaScript is a scripting language that was initially developed in 1995 by Brendan Eich , then of Netscape , for use within web pages. The standardised version is ECMAScript . To make web pages more interactive, some web applications also use JavaScript techniques such as Ajax ( asynchronous JavaScript and XML ). Client-side script

7546-462: The presence and size of a Local Color Table (which follows next if present). The image data follows: one byte giving the bit width of the unencoded symbols (which must be at least 2 bits wide, even for bi-color images), followed by a series of sub-blocks containing the LZW-encoded data. Extension blocks (blocks that "extend" the 87a definition via a mechanism already defined in the 87a spec) consist of

7644-418: The primary pronunciation, while Cambridge Dictionary of American English offers only the hard- g pronunciation. Merriam-Webster's Collegiate Dictionary and Oxford Dictionaries cite both pronunciations, but place the hard g first: / ɡ ɪ f , dʒ ɪ f / . The New Oxford American Dictionary gave only / dʒ ɪ f / in its second edition but updated it to / dʒ ɪ f , ɡ ɪ f / in

7742-444: The pronunciation to deliberately echo the American peanut butter brand Jif , and CompuServe employees would often quip "choosy developers choose GIF", a spoof of Jif's television commercials. However, the word is widely pronounced as / ɡ ɪ f / , with a hard g , and polls have generally shown that this hard g pronunciation is more prevalent. Dictionary.com cites both pronunciations, indicating / dʒ ɪ f / as

7840-454: The request and response. The HTTP protocol is fundamental to the operation of the World Wide Web, and the added encryption layer in HTTPS is essential when browsers send or retrieve confidential data, such as passwords or banking information. Web browsers usually automatically prepend http:// to user-entered URIs, if omitted. A web page (also written as webpage ) is a document that is suitable for

7938-431: The request it sends an HTTP response back to the browser indicating success: followed by the content of the requested page. Hypertext Markup Language ( HTML ) for a basic web page might look like this: The web browser parses the HTML and interprets the markup ( < title > , < p > for paragraph, and such) that surrounds the words to format the text on the screen. Many web pages use HTML to reference

8036-421: The same site; others require one form or the other, or they may map to different web sites. The use of a subdomain name is useful for load balancing incoming web traffic by creating a CNAME record that points to a cluster of web servers. Since, currently , only a subdomain can be used in a CNAME, the same result cannot be achieved by using the bare domain root. When a user submits an incomplete domain name to

8134-420: The same way. A dynamic web page is then reloaded by the user or by a computer program to change some variable content. The updating information could come from the server, or from changes made to that page's DOM. This may or may not truncate the browsing history or create a saved version to go back to, but a dynamic web page update using Ajax technologies will neither create a page to go back to nor truncate

8232-501: The sentinel, an additional byte specifying the type of extension, and a series of sub-blocks with the extension data. Extension blocks that modify an image (like the Graphic Control Extension that specifies the optional animation delay time and optional transparent background color) must immediately precede the segment with the image they refer to. Each sub-block begins with a byte giving the number of subsequent data bytes in

8330-415: The server name of the URL ( example.org ) into an Internet Protocol address using the globally distributed Domain Name System (DNS). This lookup returns an IP address such as 203.0.113.4 or 2001:db8:2e::7334 . The browser then requests the resource by sending an HTTP request across the Internet to the computer at that address. It requests service from a specific TCP port number that is well known for

8428-406: The sub-block (1 to 255). The series of sub-blocks is terminated by an empty sub-block (a 0 byte). This structure allows the file to be parsed even if not all parts are understood. A GIF marked 87a may contain extension blocks; the intent is that a decoder can read and display the file without the features covered in extensions it does not understand. The full detail of the file format is covered in

8526-625: The text, it helped to confirm the validity of his concept. The model was later popularized by Apple 's HyperCard system. Unlike Hypercard, Berners-Lee's new system from the outset was meant to support links between multiple databases on independent computers, and to allow simultaneous access by many users from any computer on the Internet. He also specified that the system should eventually handle other media besides text, such as graphics, speech, and video. Links could refer to mutable data files, or even fire up programs on their server computer. He also conceived "gateways" that would allow access through

8624-509: The third edition. The disagreement over the pronunciation has led to heated Internet debate. On the occasion of receiving a lifetime achievement award at the 2013 Webby Awards ceremony, Wilhite publicly rejected the hard- g pronunciation; his speech led to more than 17,000 posts on Twitter and dozens of news articles. The White House and the TV program Jeopardy! also entered the debate in 2013. In February 2020, The J.M. Smucker Company ,

8722-441: The two terms do not mean the same thing. The Internet is a global system of computer networks interconnected through telecommunications and optical networking . In contrast, the World Wide Web is a global collection of documents and other resources , linked by hyperlinks and URIs . Web resources are accessed using HTTP or HTTPS , which are application-level Internet protocols that use the Internet transport protocols. Viewing

8820-443: The usefulness of full-color GIFs. Additionally, not all GIF rendering programs handle tiled or layered images correctly. Many rendering programs interpret tiles or layers as animation frames and display them in sequence as an animation with most web browsers automatically displaying the frames with a delay time of 0.1 seconds or more. Sample image (enlarged), actual size 3 pixels wide by 5 high The hex numbers in

8918-449: The version, followed by a fixed-length Logical Screen Descriptor giving the pixel dimensions and other characteristics of the logical screen. The screen descriptor may also specify the presence and size of a Global Color Table (GCT), which follows next if present. Thereafter, the file is divided into segments of the following types, each introduced by a 1-byte sentinel: An image starts with a fixed-length Image Descriptor, which may specify

9016-454: The visible portion of each layer showing through the transparent portions of the layers above. To render a full-color image as a GIF, the original image must be broken down into smaller regions having no more than 255 or 256 different colors. Each of these regions is then stored as a separate image block with its own local palette and when the image blocks are displayed together (either by tiling or by layering partially transparent image blocks),

9114-465: The web pages (or URLs) the directed edges between them to the hyperlinks. Over time, many web resources pointed to by hyperlinks disappear, relocate, or are replaced with different content. This makes hyperlinks obsolete, a phenomenon referred to in some circles as link rot, and the hyperlinks affected by it are often called "dead" links . The ephemeral nature of the Web has prompted many efforts to archive websites. The Internet Archive , active since 1996,

9212-417: The working title 'Firebird' in early 2003, from an earlier practice in browsers such as Lynx . It is reported that Microsoft was granted a US patent for the same idea in 2008, but only for mobile devices. The scheme specifiers http:// and https:// at the start of a web URI refer to Hypertext Transfer Protocol or HTTP Secure , respectively. They specify the communication protocol to use for

9310-499: Was a success at CERN, and began to spread to other scientific and academic institutions. Within the next two years, there were 50 websites created . CERN made the Web protocol and code available royalty free in 1993, enabling its widespread use. After the NCSA released the Mosaic web browser later that year, the Web's popularity grew rapidly as thousands of websites sprang up in less than

9408-595: Was called 87a. This version already supported multiple images in a stream. In 1989, CompuServe released an enhanced version, called 89a, This version added: The two versions can be distinguished by looking at the first six bytes of the file (the " magic number " or signature), which, when interpreted as ASCII , read "GIF87a" or "GIF89a", respectively. CompuServe encouraged the adoption of GIF by providing downloadable conversion utilities for many computers. By December 1987, for example, an Apple IIGS user could view pictures created on an Atari ST or Commodore 64 . GIF

9506-704: Was fairly common to make GIF images using the websafe palette . This ensured predictable display, but severely limited the choice of colors. When 24-bit color became the norm, palettes could instead be populated with the optimum colors for individual images. A small color table may suffice for small images, and keeping the color table small allows the file to be downloaded faster. Both the 87a and 89a specifications allow color tables of 2 colors for any n from 1 through 8. Most graphics applications will read and display GIF images with any of these table sizes; but some do not support all sizes when creating images. Tables of 2, 16, and 256 colors are widely supported. Although GIF

9604-441: Was one of the first two image formats commonly used on Web sites, the other being the black-and-white XBM . In September 1995 Netscape Navigator 2.0 added the ability for animated GIFs to loop . While GIF was developed by CompuServe , it used the Lempel–Ziv–Welch (LZW) lossless data compression algorithm patented by Unisys in 1985. Controversy over the licensing agreement between Unisys and CompuServe in 1994 spurred

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