My computer has gone mad! Somehow i've vanished the tool bar at the top!?

I was typing along and suddenly the address and tool bar at the top disappeared! When i move the pointer up where it should be, it reappears but only when the pointer is up there. What dd i do? This has happened before and i fixed it, or at least thought i did! I tried locking the tool bar but it didn't come back. Now what/ i liked that feature always there, not having to click in the area to see it.