Why So Big
Garden Grove, California
• Cambridge, England
My guess is that you have held down the Ctrl key whilst using the mouse wheel (to try to scroll, perhaps?) Ctrl + Mouse Wheel will enlarge or reduce the size of the font on the web page. Moving your finger forward (towards the screen) on the mouse wheel will enlarge and backwards will make the text smaller. The same thing happens with the keyboard presses Ctrl+ '+' and Ctrl + '-'.
• United States
I'm not 100% sure, but it sounds like you're having issues with things on the screen being too big. If that's what's going on, try pressing control and the - button (at the top next to the 0 key) at the same time. That should make the things on your screen smaller.