page mosaic in screen

[Lóránt Lakatos]

Dear Help Personnel !
I az 77 years old.
During editing a text, because of hitting some
unwanted key combination, the displayed text
altered so, that the whole text appeared on the
screen as a mosaic of the pages.
How can I withdraw this in order to get only
the desired one  page on the screen?
Thank You
Lorant Lakatos