I am having a problem with drop down menu hiding behind flash in
most of the sites I have developed especially using Mozilla.Any ideas,hacks?

Make sure you read the whole thread:
http://www.daniweb.com/techtalkforums/thread73830.html

Just use a different menu.
http://www.dynamicdrive.com/style/
Im sure you'll find one you like there

Thanks guys,i tried some of the codes you suggested and it worked.