It shouldn't do that... try deleting the Cache.db file.
Open the Finder. From the Finder menu bar click Go > Go to Folder
Type this exactly as you see it here:
Click Go then move the Cache.db file to the Trash.
Quit then relaunch Safari for changes to take effect.
This do some help But still choppy I noticed that not every website has this suitation some are smooth but some are choppy especially this http://www.3dmgame.com But when i switch to chorme No websites have this situation There must be some bug in safari PS: i didn't have this problem in 10.6 and 10.7