My Posts and Popular Posts Keep Changing

Hi,
I am brand new to autoblogging, in fact someone else set me up with this blog. Anyway, my tags keep changing and returning. I delete the tags from my tags and popular tags area and they pop up again, later. I especially have had difficulty with the tag “auctions” I have gotten rid of the tag and the posts that come along with it, but the tag and the posts with auctions in it keep coming back. How do I get rid of the changing tags, especially the tag “auctions”. My front page is static but the blog isn’t. Your help is much appreciated. Thanks.