To turn on private browsing:
Choose Safari > Private Browsing, and click OK when you see a confirmation message. To skip the confirmation message, hold down the Option key while you choose Private Browsing.
When private browsing is turned on:
Webpages are not added to the history list.
The Downloads window is cleared so the name of anything you downloaded won't appear in the list. (To get rid of the downloaded item itself, you must delete it.)
Information isn't saved for AutoFill, including names and passwords.
Searches are not added to the pop-up menu in the Google search field.
Cookies are deleted.