Cascading Style Sheets are a necessary ingredient for, and one of the key components of, DHTML. They’re also a good idea for managing Web pages in general.
Before you begin using CSS though, there are a couple of guidelines you should know:

CSS is very finicky about syntax. One misspelling, one misplaced semi-colon and the whole thing can go kaput and not reflect your chosen attributes.

Different browsers react just a bit differently with CSS styles. The following link will show you the syntax that works best across different browsers. If you follow these syntax guidelines you’ll find it easier to design CSS to work across different platforms.

Read the “Twelve Dynamic HTML Lessons”