The popup would have to do an AJAX call, or you'd have to push all your info down in your initial HTML. Beyond that, it's just a popup.
Much as I loathe it, the ASP.NET AJAX library has
this[
^]. Personally, I'd view the source to learn how to do it myself. It looks to me like it just uses mouse over and mouse out events. You could fire a timer in mouse over to make it wait for a hover.