From what I understand, not so much pages that you have visited, because Google has limited access to that information, basically sites you have visited from clicking their search results.
But if you are logged in, Google will account for social signals in the results it gives you. So pages that you have G+'ed or tweeted, or have been shared by somebody you follow on Google+. Their latest push is integrating GMail into search, which I assume means that it will try to look at your contacts and any information it can find from or about them to determine which results to show you.