The site may be saved as a "Favorite". When a site is bookmarked in FF or Favorited in IE the site will not be erased from the history when everything else gets cleaned up.
What you need to do to erase it is go into your "Favorites" folders. Look for that exact site and then manually delete it from there. That will get rid of it.
Yes i know this, so i removed ALL my facorites manualy and when i type in "PO" POR* still pops up in the history. can anyone please help me