Hi i saw on many web sites. peoples are using same ad units on the same page like; 336x280 and 336x280 on the same page 160x600 and 160x600 on the same page does it breaks the adsense tos?
No.You can use whatever 3 ad units you desire(doesn't matter if they are the same type) + 1 ad link unit on one page.Also , you can put the google refferal buttons .