How do i change my web's font size back to its original size?

my son started mashing buttons on my keyboard....over in the upper right corner. All of a sudden my font got really tiny. i looked up the problem on here but going to view and changing the font size doesn't work...it still says what i originally had (medium) so i can't figure out how to get it back. Also some webpages i go to only shows like its a minimized window in the left corner but its not the outside will be white.How do i change my web's font size back to its original size?
if your mouse has a wheel on the top, hold down your Ctrl key and scroll up to enlarge font, down to decrease font.

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