This week's Macworld OS X Hint
Safari has a private browsing features that greatly limits the "tracks" you
leave when
browsing the Web. When in private browsing mode (Safari -> Private Browsing),
Safari won't
add Web pages to the history file, removes things from the Downloads window,
won't save
autofill information, and won't add searches to the pop-up menu of recent
searches.
http://www.macworld.com/article/133941/2008/06/safariprivate.html?lsrc=mwhints