When you visit a colleague's webpage, do the new articles she's posted jump out at you? When you return to your favorite news website, is it easy to find the front page story you saw yesterday? The Web is a dynamic, ever-changing collection of information, and the changes can affect, drive, and interfere with people's information seeking activities. With so much information online, it is now possible to capture and study content evolution and human interaction with evolving content on a scale previously unimaginable. This talk will use large-scale log analysis to explore how and why people revisit Web content that has changed, and illustrate how understanding the association between change and revisitation might improve browser, crawler, and search engine design.