hello, try to press ctrl+0 ('zero') while you're on the page in order to reset the zoom level or in case this doesn't work also go through the other common troubleshooting steps at Websites look wrong or appear differently than they should.

Note that keyboard shortcuts may not be working if a plugin has focus.

In such a case you need to click elsewhere or use the View menu (press F10 or hold down Alt to make the menu bar appear)

• View > Zoom > Reset (Ctrl+0 (zero); Command+0 on Mac)

• http://kb.mozillazine.org/Zoom_text_of_web_pages