i cant find safari on my computer, i dont know what happened to it where can it back?

Safari comes as a part of OS X. It cannot be installed individually. If you can't find it in Applications or Trash or using Spotlight, you'll have to run the OS X update again. Back up your system using time machine first. But I don't think you can delete Safari because it is so tied to OS X. It is probably on your system in a folder you don't expect. Accidental move most likely.

christina --

In your dock (the bar with all your apps) can you see the little rocketship in the circle? That's your Launchpad. Double click on that, and look for Safari. If it's not there, click on the hard drive icon (upper right hand corner), and click on Applications. Is Safari icon in there?