html - Drop down menu blocks links on main page -

i have iframe containing drop down css menu @ top of pages , blocking links or hrefs being clicked in area directly below drop down menu. within height of menu obviously.

this happens in firefox , not ie10. (weird ....usually problems reverse)

i have been looking solution time without success. related iframe or 2 items in same space?

it's not z-axis thing either unless i'm missing something. advice appreciated.