Keep download times as short as possible. No one likes to wait for unnecessary or unnecessarily large graphics to download. Clean code, a minimum of tables, and small graphics will ensure that your viewers don't get frustrated and leave your page before they even see it. Make the site easy on the eyes. It's harder to read text on a monitor than on paper.
Background images decrease the contrast between the background and print.
A white background with black text works. Animation and marquees distract the eye and should also be avoided unless it's the only way you have of presenting the information. Keep in mind that some fonts are easier to read than others and not everyone has the same fonts on their machines as you do. Avoid the use of frames. Frames introduce problems for users wanting to print or bookmark your pages.