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I think the answer your looking for is in the very link you provided http://googlewebmastercentral.blogspot.in/2012/08/website-testing-google-search.html Do not redirect only bots.... This is seen as deceptive and will get you a nice penalty. 302 is a good solution.  Just make sure you do it with the same frequency you do for a real person... no special handling for google bot. If you prefer one version remain indexed over another version, use the rel=“canonical” link attribute