Hello, I am moving from one forum software to another, i currently have about 2400 forum posts listed on Google that will all 404 once i change to the new forum. Should i block the forum with robots.txt now so they get removed from Google or should i just accept i will have a lot of broken links on Google for a while? Also will this affect the rankings of the rest of my site in Google? Thanks
You should block them from robots.txt and then remover those urls from google index using google webmaster tools..