Did you accidently hold CTRL and scroll up or down with your mouse? This changes the size of font ect. Also, Have you tried
restarting your browser? If you didn't, try that, it might reset it back to the way it was before this happened. Besides posting
in the video, your sure there aren't any settings you could have accidently messed with? If not, go to your Internet Options
and reset everything back to default settings. Keep me updated!

~Marc