unwanted, unhelpful 404 errors

Hey all – I launched a site last week and since then I’ve been getting an increasing number of 404 error notices emailed to me…problem is, they’re all for things like images I had up on a draft page and then took down, or for various css files and other things within wp-content. I have not gotten a single one that was because a real person was trying to get to something that should have been there but wasn’t. They all look roughly like this:

Someone, probably a legitimate user, tried to go to
http://mydomain.org/wp-content/themes/mytheme/images/imageitookdownaweekago.jpg and received a 404 (file not found) error. It likely wasn’t the visitor’s fault, so please try to fix this as soon as possible.

Any ideas about what happening or what I can do to make it stop? I don’t want to filter out all 404 errors in case a legit one does show up at some point, but this is getting ridiculous…literally dozens per day. Any help would be greatly appreciated. Thanks so much…