One common concern with optimization is that testing content will bring down SEO. In actuality, testing will not affect SEO.
Here’s what happens, a regular visitor goes to the web page and sees an experiment, which is a version of the tested page. Google’s spiders go and only see the default content, meaning what existed on the page previously (or whatever you want default content to be.)
What a visitor and Google spider see:
Don’t believe me? Here are some quotes from two industry folks that know their stuff:
Basically conversion testing is a legal form of cloaking. What you’re really doing is showing a bunch of different versions to people to find the best one, but you’re only showing one version to the search engines.
Rand Fishkin, CEO of SEOmoz
Tom Leung, business product manager of Google Optimizer
You should worry about if what you’re testing will be good for SEO or not though. And what’s good for SEO is a slightly bigger topic… (understatement.)
Quotes from bruceclay.com.