I had a need for a tooltip class that was lightweight and had the features I needed. I had trouble finding anything in ActionScript 2, but I found a good one in ActionScript 1, ported it to ActionScript 2, and added a couple features that I needed. With the permission of the previous author, I am making my modifications available.
I have to say that one thing that has always bugged me about Jakob Nielsen’s web site is the complete lack of visual aesthetic. The impression that I get from his site is that good usability means ugly web design. Contrary to that impression, I believe that by applying standard visual design principles such as grouping content, making headlines that are easy to scan, and using white space to guide the user’s eye, usability can be significantly enhanced.