Hi, not sure why this happens and apologies if this has been posted elsewhere ( I have looked but cannot find it) I have a website (about 3 years old) and over the past week several pages have now started appearing without the www. in the search results (and also further down than the with www). The cache page (of the same search results) without the www show an error code by Google.. Any suggestions? I have now added a mod-rewrite to send the non www to www only but not sure IF this is the answer.
Yes, you're on your way to a fix. Just make sure your rule indicates a 301 HTTP status for the redirection. If you don't intentionally set the status code as 301, you will most likely get a 302 and the without-www urls will not be removed from the index.