My screen keeps stretching out pls help?

My daughter got on my computer (she's 2) while i was making breakfast.. now the screen keeps stretching. When i run the mouse over up the top 'bar?' the sites pop up until i take the mouse away then back to stretch... It's panging me off and i can't seem to fix it.. im not very computer literate. Please help me someone!!!! I think the part that keeps hiding is the 'browser'? i dont know it's where i write google and stuff : (