Hi,
We should separate your question into two parts.
First, you mentioned you want the control be added to the webpartzone randomly, not by choosing which zone to add. But I think the catalogzone is for re-displaying the webpartzone which has been closed by user or displaying some other controls which is not visiable when page loaded , the choice provided to the user is reasonable. If you want to show all of your webpartzones by random order(just like the portal site you memtioned), you could write some code to achieve that, even not need to use catalogzone.
Second, if you want to make your webparts work in FireFox, here's the sollution you may refer.
http://weblogs.asp.net/scottgu/archive/2006/01/20/436034.aspx
Thanks.