Markup languages (such as HTML, XHTML and XML)
Style sheet languages (such as CSS and XSL)
Client-side scripting (such as JavaScript and VBScript)
Server-side scripting (such as PHP and ASP)
Database technologies (such as MySQL)
Multimedia technologies (such as Flash and Silverlight)
Use semantic markup that provides a meaningful structure to the document (i.e. web page)
Use a valid markup language that conforms to a published DTD or Schema
Provide text equivalents for any non-text components (e.g. images, multimedia)
Use hyperlinks that make sense when read out of context. (e.g. avoid "Click Here.")
Use CSS rather than HTML tables for layout.
Compatibility and restrictions
For the typical web sites, the basic aspects of design are:
Multidisciplinary requirements
Pixel measure results in fixed or static content
Em measure results in proportional content that is relative to font-size
Percent measure results in fluid content that shrinks and grows to "fit" display windows