I am lost in map. Grey screen.

i am a newbie of unity. while i was going around the blank map (i don’t know i just did) i decided to go up and all of a sudden, white frames were gone. where ever i looked, it was all grey. i added terrain or similar objects so i could get where i am but they just didn’t show up. uninstalling didn’t help either. what should i do?

ooooh god! thanks!