When working with CSS, keep these two tips in mind: simplify and verify.
After you’ve crafted your CSS rules, simplify them by using only the selectors and properties you believe you need; any extras could cause some confusion down the road. Then verify the HTML, XHTML, and CSS with the help of validators as you code. Those two steps solve most problems developers encounter when working with CSS.
However, if you still run into trouble, this appendix contains some of the top references, discussion groups, and tools on the Internet to help in your CSS development.