Mobile Safari in iOS 5 adds the ability to browse the web in “private browsing” mode. When you enabled private browsing in Safari, your browsing history, web cookies, cache, logins are not saved. Thus private browsing mode leaves no trace of your online activity to be discovered by prying eyes.
To enable private browsing mode, look for Safari under Settings app. Turn on the switch for “Private Browsing”.
With private browsing enabled, Safari browser switches from the normal blue color to a cool black, a great visual reminder that you are in a somewhat safer browsing environment.