Today I got an email from Google Webmaster Tool, telling me that there are a lot of server errors in my site as detected by Googlebot.
I checked the errors and I found that all the errors are related to hundreds of links which were once on a prettyURL format. But I used prettyURL mod 3 years ago. I had uninstalled it long, long time ago.
So now I found that thousands of my indexed pages in Google are still in prettyURL format. How shall I remove these prettyURL permalinks from Google?
How shall I tell Google not to index or visit these non-existent prettyURLs pages of my forum?
Naturally, Google would get a server error when it crawls these non-existent forum pages/links.
Apologies for not replying sooner...
I've been running through this, in my "Fluffy" head.
I'm wondering, now, if you might get the best advice, for this, by posting in that mod's support topic.
I can see why you posted, here. But, as nobody's come-up with anything, thus far, I'd suggest that you try the mod's topic to see what comes-up. :)
Try installing the "revert" package from http://code.google.com/p/prettyurls/downloads/list. Otherwise, Google has no way of knowing that those were just rewritten versions of still-existing URLs, and as long as you still have old links floating around somewhere (either in old posts or in links from other sites), Google will just complain that they're not working.