As you know, fluctuations in search results happen all the time; the web is constantly evolving and so is our index. Improvements in our ability to understand our users' interests and queries also often lead to differences in how our algorithms select and rank pages. We realize, however, that such changes might be confusing and sometimes foster misconceptions, so we'd like to address a couple of these myths head-on.

Myth number 1: Duplicate content causes drops in traffic!
Webmasters often wonder if the duplicates on their site can have a negative effect on their site's traffic. As mentioned in our guidelines, unless this duplication is intended to manipulate Google and/or users, the duplication is not a violation of our Webmaster Guidelines. The second part of my presentation illustrates in greater detail how to deal with duplicate content using canonicalization.