In iOS 5 Beta 7, Safari now has a 'Private Browsing' feature that I was unaware of in previous versions. Access through Settings / Safari / Privacy, having this feature enables a Black UI in the Safari app and hides your history when in use. The 'Clear Cookies and Data' box is now as one instead of two separate buttons. Sorry if I skimmed over this find previously and/or if this is the wrong category. Actually on further inspection, this has been here since Beta 1!