display screen done 90 deg turn

Hi,
Whilst on my laptop I in advertantly must have touched/pushed some keys at the bottom of keyboard eg alt, windows key, ctlrl on r/h side of keyboard.
All of a sudden my display on the screen done a 90 deg turn.( a bit hard to operate) :mad:
Would much appreciate some advice/help so the display can be restored as it should be.
Many thanks for any assistance.
enigmatic_5