What is HTML? Hyper Text Markup Language (HTML) is the main markup language for creating web pages and other information that can be displayed in a web browser. HTML elements form the building blocks of all websites. HTML is written in the form of HTML elements consisting of tags enclosed in angle brackets (like <html>), within the web page content. The purpose of a web browser is to read HTML documents and compose them into visible or audible web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page. HTML allows images and objects to be embedded and can be used to create interactive forms. HTML gives authors the means to:

  • Publish online documents with headings, text, tables, lists, photos, etc.
  • Retrieve online information via hypertext links, at the click of a button.
  • Design forms for conducting transactions with remote services, for use in searching for information, making reservations, ordering products, etc.
  • Include spread-sheets, video clips, sound clips, and other applications directly in their documents.
What is XHTML? XHTML is a variant of HTML that uses the syntax of XML, the Extensible Markup Language. XHTML has all the same elements (for paragraphs, etc.) as the HTML variant, but the syntax is slightly different. Because XHTML is an XML application, you can use other XML tools with it (such as XSLT, a language for transforming XML content). What is CSS? Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation semantics (the look and formatting) of a document written in a markup language. Its most common application is to style web pages written in HTML and XHTML, but the language can also be applied to any kind of XML document, including plain XML, SVG and XUL. CSS is independent of HTML and can be used with any XML-based markup language. The separation of HTML from CSS makes it easier to maintain sites, share style sheets across pages, and tailor pages to different environments. CSS can also allow the same markup page to be presented in different styles for different rendering methods, such as on-screen, in print, by voice (when read out by a speech-based browser or screen reader) and on Braille-based, tactile devices. CSS specifies a priority scheme to determine which style rules apply if more than one rule matches against a particular element.