My Website Is Displaying in Miniature!

I accidentally pushed something on my keyboard to make everything on my website, including the dashboard and login page, display in miniature! Does anyone know what keys I pushed to cause such an effect? It won’t go away! You can’t read anything at my website, everything is too small. Please tell me how I can reverse this. There has to be a zoom in and out button on my keyboard. I’ve tried looking it up, but haven’t had any luck. I’m using Windows XP.