I came across a great article on tooltips for persistent browser based games. In the article Vindexus shows how to use the BoxOver script to enhance PBBGs with tooltip functionality. His sample uses the box over script and the title of span tag. A good example of using simple pre-existing html tags to enhance the gaming interface.

I am working on including this functionality in my current PBBG The Knights of the Realm 2 and will also incorporate it into my other game. The use of tooltips does provide a great feature for users. I may incorporate a way to turn the tooltips on and off as well.