C SS is an excellent addition to plain HTML. W ith plain HTML you define the colors and sizes of text and tables throughout your pages. If you want to change a certain element you will therefore have to work your way through the document and change it. W ith CSS you define the colors and sizes in " styles". Then as you write your documents you refer to the styles.
A web style sheet is a form of separation of presentation and content for web design in which the markup ( i. , HTML or XHTML) of a webpage contains the page' s semantic content and structure, but does not define its visual layout ( style).