Depends also on the site hosting, whether or not Ajax is installed and turned on or not in the case of ASP.NET AJAX...otherwise depends what Ajax library(ies) one uses for the menu.
What you want would require a custom-written module -- I am not at all an Ajax expert, I've just simply read about it -- but I also recommend you use a library that can be externally loaded and kept up to date, like the Yahoo and Dojo ones (I think), for example.
HTH Tom |