FIREFOX KIOSK MODE.
Could be in full screen mode too.
I'm posting this for a less-computer-literate friend. She just got her first laptop. It has Win & Home Premium installed. It seems to be working fine. She installed Firefox last night, and this morning she may have hit a wrong key or something. She's not able to see everything she should be able to on her screen. She can't see anything above tabs, incl. the search/back/forward line (yes, my computer literacy is limited & I'm forgetting terms) and the top line which includes tools, help etc.
She's tried restarting Windows, and changing her FF theme, with no change.