Soundguy brought to my attention that search engines that visit UMD are visiting links on this site, including the ads. This caused your advertising credits to be expended unnecessarily, and apparently the search engines are ramping up their visitation rate, making this a real problem. Not too long ago, I updated UMD to not deduct credits from an ad that was "clicked" by a search engine. The link will still work however, and UMD will still send your site this search engine traffic (and still donates the pagerank weight). It's just that credits will not be deducted.

Today I verified that it's working, because I am notified whenever a bot does click a link. Google just hit up 5 ad links this morning at the same time, and UMD did not deduct any credits.

Just a heads up.
MM