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Hoping someone can answer these questions. We've got some AJAX coding on our site too and I'm concerned it's going to cause a lot of indexing problems. The obvious answer is to see if you can find another way to build your site where it will be viewable, but often times (and in my case too) that isn't possible from a development standpoint.

Oh, duh. missed the dropdowns. Not your UI, just me multi tasking. Thank you!

So they clearly have ways of detecting bounces across a variety of methods (return to SERP, GA, toolbar). I have seen no evidence that they use this directly as a ranking factor. It seems pretty noisy / easily gamed and also not desperately well-correlated with quality (as sometimes if you are just looking for a phone number for example, a bounce is the desired behaviour). I think they are using usage data of a variety of kinds to measure and improve the algo, but I'm not convinced it factors in directly from bounce rate itself. Hope that helps.