You could create a hidden input field in default.aspx and set it's value to the TabID (via vb).. Then in javascript, you look for the object and grab it's value to determine the TabID....

Sanjay

or this

http://www.dotnetnuke.com/Community/Forums/tabid/795/forumid/109/threadid/246703/scope/posts/Default.aspx

I was trying to display specific image on specific page and solved the problem like above.

You can do something like this.

 
 var AncestorID = <(percent Mark)= PortalSettings.ActiveTab.ParentId (percent Mark)>;

The external javascript should be a "function" so you can pass the CurrentTabID to the function.

*(percent Mark) < replace it with %. some reason i couldn't put it there.