Massive amount of 404s after forum prune

[TheTippingPoint]

So I pruned my vbulletin forum the other week and now webmaster tools detects over 4000 urls as not found.  Is there a solution to this?  Is this something that could negatively effect rankings?  Any ideas?

[AlanMosley]

If they are simply urls that are in the index, they will go away after a few weeks. but if there are links pointing to the deleted pages either internal or external, then you need to take action.

For interal links you should delete the links, for external you should 301 thenm to a relative page