My Mac freezes when using Safari I am using a Mac with OSX Snow Leopard. 
Sometimes I am playing some media through Safari and my Mac freezes. I basically cannot do anything. The trackpad does not work anymore as well as the keyboard. The only solution is to restart the system.

The question is:

Why the system suddenly freezes? Is the any way to prevent it? Or is there any way to avoid restarting the system every time?
This is a common Flash interaction issue (sounds like). I use the Safari extension ClickToFlash so I can control what Flash runs and when. And, I also use AdBlock to be sure those pesky side Ads don't bother me. You can still run Flash, but you have control and the freezing will hopefully stop.