Remove pages from index

[kaus]

I have some pages that are indexed that are no longer valid so of course I am getting 404's. I have deleted them from my ftp however they are still showing up in my errors in the webmasters tools. There are now 28 of them and I am not sure if I should be concerned of this or not. Any help would be appreciated and should I worry with having 404 errors for pages that no longer exsist or will they eventually drop off?

[geoffvro]

If you moved them, than use a redirect to maintain pagerank. If they're gone for good than disallow search engines from searching those pages in your robots.txt file.