A good style will ensure your visitors can navigate easily throughout your site. They will be able to read all of your text and see all of your graphics. Most importantly, they will be able to easily gather all the information you wish to provide. Yale Style Manual is an excellent place to learn about web style. Color Communicate with Color discusses the importance of color in webpages.
Webpages are visual tools.
If you do nothing to them, the pages are gray with black text. This does not normally help the visitor absorb the material you are presenting. Visibone Color Lab will help you decide what colors look good on your pages. Visibone will let you test it on their pages before anyone sees it on yours. Specifying what font face will be used to display your text or headers on your webpage is one way to use fonts.