Hi
I'm having the same problem and I don't think that ImageButton would solve the problem. Map area means that image would have many buttons   . In my case over 1000.

I'm currently working on a work around class, such as:
http://www.codeproject.com/useritems/HtmlMap.asp

It seems that MS is trying to hide JavaScript and html possibilityes...

dg to excel and field format
I'll buy you a latte....
Can I embed an IE control in a webpage?
Retrieving values from dynamically added controls
Visual Studio 2005 -- Multi-Tabbed Control