How does Google handle pages with content that changes on each page load?

Matt's answer:

Today’s question comes from Brian Webster in Ames, Iowa. Brian wants to know “How does Google handle pages that have some content that changes each time the page is reloaded? For example, a random tip about the given topic as a sidebar on the page, or a random image on the page.” Great question and the short answer is, when we crawl a page, we basically know that snapshot that we fetch on that particular instant in time. So if you’ve got something that rotates through, we might not necessarily see it. So, as a result, the take away is, if you’ve got like five links and you really, really care about one of those links, maybe take that one out of the rotation and make sure that it’s always on the homepage. And then you can rotate between the four different images or the four different quotes or the four different elements in the side bar. But at any given time, we’re going to follow a link, we’re going to fetch that page and we’re basically going to treat that as a snapshot, frozen in time. So over time, we might learn things like oh, this page has got some content that changes right here. But in general, I wouldn’t necessarily count on or rely on Google being able to hit reload enough that we know oh, here are all the links from a web page that are rotating in and out regularly. Instead, if you’ve got some important links that you really want Googlebot to see and follow, I’d make sure that those links are always on your root page or the various web pages that you’ve got being crawled by Google.

by Matt Cutts - Google's Head of Search Quality Team

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