And finally, if you're using JavaScript to display critical navigation tools or information, make sure those elements are accessible to folks whose browsers can't run JavaScript. Older browsers can have a lot of problems running JavaScript, and certain browsers for the handicapped can be problematic as well. And finally, some people don't like JavaScript, and simply turn it off in their Web browser. If you re designing something for a general audience, keep this in mind and try to avoid using the function. If you insist on using it, give people are warning as to what browser they should be using, or forward them to a non-JavaScript page.
Browsers tend to have problems with scripts included in the body area.