my computer was zooming in and out for no reason and now it's stuck zooming in on youtube and I can't zoom it out!!

I was watching a video on youtube and when I scrolled down to see the comments with my mouse the screen zoomed out!! when I scrolled up the screen zoomed in to much!! my screen on youtube is now stuck zoomed in to much so I can't see anything!! my mom tried fixing it and so did my dad!!Help Please!!