What is CSS, Ajax and Web 2.0

First to define what CSS, Ajax and Web 2.0 are and how they apply to web sites. For this I'll turn to the Wikipedia definitions of each term.

CSS, short for Cascading Style Sheets, is a style sheet language used to describe the presentation 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 be applied to any kind of XML document, including SVG and XUL.

Ajax, (the programming language, not the cleanser) short for Asynchronous JavaScript and XML, is a web development technique for creating interactive web applications. The intent is to make web pages feel more responsive by exchanging small amounts of data with the server behind the scenes, so that the entire web page does not have to be reloaded each time the user makes a change.

Web 2.0 is a phrase coined by O'Reilly Media in 2004 which refers to a supposed second generation of Internet-based services - such as social networking sites, wikis, communication tools, and folksonomies - that emphasize online collaboration and sharing among users.