How to auto zoom in imac ???

Hi, my name is Stephen. and i'm using the newest imac. and the problem is everytime i put data using number (iwork) for accounting, the font is very very little almost unable to see by normal. i must pinching my eyes a little bit to see it clearly. do you guys know how to solve this problem ? should i change something in setting ? and how ? and this is happen when using safari too. from the first time i bought it i never change the setting except to change username and password to login in. so i let it all in default version. i'm using imac 27-inch, Mac OS X Lion 10.7.4 processor 3.1GHz intel core i5. nothing changed since i bought it till now. Please help me, it's very annoyed and difficult for me to input, edited, even read it as report.