Text Zoom by accident -- something to do with touchpad

I had an email open and went down to the programs bar at the bottom, hit the left click on the touchpad and then my right hand hit something -- maybe the touchpad??  Then this dialogue box came up saying "text zoom" and went to 120%, then faded away.  It looks like ONLY my email replies have been changed though.  But I have big text on all my email replies now.  How do I undo that?  Is there a function of hitting the touchpad and another key that changes the font size?