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Use a canonical tag or apply noindex/nofollow to Content Experiment variations to prevent duplicate-content issues.
While your Content Experiment is running, you should prevent the page variations from being indexed in the search engines to avoid any duplicate-content issues that could hinder your SEO efforts. Even though the search engine spiders may not be able to execute the JavaScript that redirects from the original page to a page variation in a Content Experiment, the spiders still may find the variations (and certainly will if the variation URLs receive any external links).
You can take two approaches: canonical or noindex/nofollow.
The advantage of rel=”canonical” is that any link equity from external links to the variation URLs will be transferred to the original URL. The disadvantage is that Bing/Yahoo may not recognize the canonical tag.
Noindex/nofollow, applied either as a page tag or in robots.txt, is universally recognized, but will negate any link equity from external links to the variation pages.
You can decide which of the two approaches would work best for you. In either case, these can serve as temporary measures, since you can (and should) apply hard 301 redirects to your content experiment pages once a test concludes and you have moved the winning variation to the original URL.
