Although CSS was first introduced in the mid 1990s, it did not become a mainstream tool among web designers and masters until more recent years. This is unfortunate, because there are millions of poorly designed web sites cluttering the internet that could be easily improved with the help of CSS.
So what exactly is CSS? CSS is an acronym that stands for Cascading Style Sheets. The term Cascading Style Sheets implies two things. First off, the style sheets are cascading. This means that multiple style sheets can be used for a single web page. Additionally, the term “cascading” also refers to the way a style is determined in the event that more than one rule matches a single element. The second thing that is implied by the name Cascading Style Sheets is that the purpose of CSS is to style web pages. Whereas the purpose of HTML (or XHTML) is to define the structure of a web page, the purpose of CSS is to define the presentation.