My toolbar and address bar have disappeared.?

Whilst typing my stupid long nails have hit a key on my keyboard that has made the toolbar and address bar at the top of my screen disappear, as well as the time and stuff thats ment to be on the bottom task bar ,the top one only comes back when I put my mouse at the very top of the screen,and go away again when i move my mouse...GRRRR what have I done?? How do I get them back?? Silly silly me....!!!!