I recently completed a volunteer redesign project for a local non-profit pet adoption center. Before doing the redesign I found that their old webmaster had put tons of hidden text at the bottom of every page, unbeknownst to the owners of the adoption center.
Now the redesign is complete and none of the new pages have spam. I see that the old pages still show up on google though. I'd like to 301 redirect them to their appropriate replacements, but I don't want to transfer any "negative opinions" google may have of those spammy pages over to the new pages. I could simply delete the spammy pages but then they'll give 404 errors to anyone who legitimately lands on them.
Anyone have any thoughts on what the best way is to handle the situation?
Meanwhile, the site shows up well in google for their terms, so if there's been a penalty it's not extremely obvious to me. I signed up for webmaster tools and there are no notifications about problems with the site. So maybe they flew under the radar, I don't know.
Those old pages only have the possibility of value if there are external links to them - no external links means no value (although they can hang around in search results for some time). There are a number of third party tools that will allow you to find whether pages have external links to them (have a look at this post in the link development forum if you need some pointers: Best way to check for backlinks? [webmasterworld.com]
As spam rarely attracts any decent links, the most likely possibility is that you won't retain value via 301s, but you will incur risk. If that's the case, just remove the pages and let them die.
If the pages rank, then it's a slightly different question, as a 301 is the quickest way to move content and retain rankings, but otherwise you may as well play it safe.
404 them, but make a custom 404 page - make it match the site theme and include a witty 404 message, full navigation suite, a list of the most popular pages and a search box. That way, anyone who does manage to get to them will have somewhere to go :) But I think you will be surprised how little traffic they get...