Google Still Crawls Dead Links

Hi!

I like to know the explanation. I setup a Google Sitemap and from the statistics that still Google indexing dead links frequently and list errors. However I deleted from Automatic Controller System at http://services.google.com:8882/urlc...&lastcmd=login. Google deletes them - sends the report to my mailbox - but after some days Google tries to index those pages again. Why does it happen? Any answer? How to stop Google indexing old pages?

Actually 10 - 15 URLs been deleted. The pages which were 1.5 years before, obviously they are no more.

Waiting for an answer from friends.