From Wikipedia, the free encyclopedia
WorldWideWeb for NeXT computer was the first browser (1991)
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A web browser is a software application which enables a user to display and interact with text, images, videos, music, games and other information typically located on a Web page at a website on the World Wide Web or a local area network. Text and images on a Web page can contain hyperlinks to other Web pages at the same or different website. Web browsers allow a user to quickly and easily access information provided on many Web pages at many websites by traversing these links. Web browsers format HTML information for display, so the appearance of a Web page may differ between browsers.
Some of the Web browsers currently available for personal computers include Internet Explorer, Mozilla Firefox, Safari, Netscape, Opera[2], Avant Browser, Konqueror, Google Chrome, Flock, Arachne, Epiphany, K-Meleon and AOL Explorer. Web browsers are the most commonly used type of HTTP user agent. Although browsers are typically used to access the World Wide Web, they can also be used to access information provided by Web servers in private networks or content in file systems.
[edit] History
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The history of the web browser dates back to late 1980s when a variety technologies laid the foundation for the first web browser, the WorldWideWeb, by Tim Berners-Lee in 1991, which brought together a variety of existing and new software and hardware technologies.
Later on, various web browsers from companies like Microsoft, Mozilla, Netscape, and recently Google emerged into the browsing world.
[edit] Protocols and standards
Web browsers communicate with Web servers primarily using HTTP (hypertext transfer protocol) to fetch webpages. HTTP allows Web browsers to submit information to Web servers as well as fetch Web pages from them. The most commonly used HTTP is HTTP/1.1, which is fully defined in RFC 2616. HTTP/1.1 has its own required standards that Internet Explorer does not fully support, but most other current-generation Web browsers do.
Pages are located by means of a URL (uniform resource locator, RFC 1738 ), which is treated as an address, beginning with http: for HTTP access. Many browsers also support a variety of other URL types and their corresponding protocols, such as gopher: for Gopher (a hierarchical hyperlinking protocol), ftp: for FTP (file transfer protocol), rtsp: for RTSP (real-time streaming protocol), and https: for HTTPS (an SSL encrypted version of HTTP).
The file format for a Web page is usually HTML (hyper-text markup language) and is identified in the HTTP protocol using a MIME content type. Most browsers natively support a variety of formats in addition to HTML, such as the JPEG, PNG and GIF image formats, and can be extended to support more through the use of plugins. The combination of HTTP content type and URL protocol specification allows Web page designers to embed images, animations, video, sound, and streaming media into a Web page, or to make them accessible through the Web page.
Early Web browsers supported only a very simple version of HTML. The rapid development of proprietary Web browsers led to the development of non-standard dialects of HTML, leading to problems with Web interoperability. Modern Web browsers support a combination of standards- and defacto-based HTML and XHTML, which should display in the same way across all browsers. No browser fully supports HTML 4.01, XHTML 1.x or CSS 2.1 yet. Currently many sites are designed using WYSIWYG HTML generation programs such as Adobe Dreamweaver or Microsoft FrontPage. Microsoft FrontPage often generates non-standard HTML by default, hindering the work of the W3C in developing standards, specifically with XHTML and CSS (cascading style sheets, used for page layout). Dreamweaver and other more modern Microsoft HTML development tools such as Microsoft Expression Web and Microsoft Visual Studio conform to the W3C standards.
Some of the more popular browsers include additional components to support Usenet news, IRC (Internet relay chat), and e-mail. Protocols supported may include NNTP (network news transfer protocol), SMTP (simple mail transfer protocol), IMAP (Internet message access protocol), and POP (post office protocol). These browsers are often referred to as Internet suites or application suites rather than merely Web browsers.
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