Google: Understanding drops in traffic

[djbaxter]

Traffic drops and site architecture issues
by Luisella Mazza, Google Search Quality Senior Analyst
Monday, June 29, 2009

Understanding drops in traffic
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!
Myth number 2: Affiliate programs cause drops in traffic!

See original article for videos with answers and more information.

...

In conclusion, remember that fluctuations in search results are normal but there are steps that you can take to avoid malicious attacks or design and architecture issues that might cause your site to disappear or fluctuate unpredictably in search results. Start by learning more about attacks by hackers and spammers, make sure everything is running properly at crawling and indexing level by double-checking the HTML suggestions in Webmaster Tools, and finally, test your robots.txt file in case you are accidentally blocking Googlebot. And don't forget about those "robots.txt unreachable" errors!

...more