A Google Webmaster Help thread has a new topic that I never covered before in my (almost) 6 years of covering SEO forum threads. A Webmaster was using a server response code of 300, which is a response of "Multiple Choices." What does that mean? The W3.org explains:
The requested resource corresponds to any one of a set of representations, each with its own specific location, and agent- driven negotiation information (section 12) is being provided so that the user (or user agent) can select a preferred representation and redirect its request to that location.
I believe that this status code tries to communicate to the browser or useragent that there can be multiple redirects for the page you landed on (i.e. multiple choices). So how does Google or other search engines handle it?
Well, it seems like Google doesn't like it and may consider some of those pages as duplicates. The Google Webmaster Help thread has JohnMu from Google who explains the issue:
Yes, we index these since they're not clear redirects and sometimes have multiple links on them ("multiple choices" :-)).
If the web server is set up to serve these, you could: - create clean 301 redirects for URLs that have changed - modify the template to have a "noindex" robots meta tag
The first is really preferred, especially when you change the URLs on your site.
Forum discussion at Google Webmaster Help.