I have a situation where Google is crawling our site.  That is fine, no problem, but the issue is that the crawler is creating URL paths that do not exist.   /events is a root folder on our site.  Googlebot is then creating URLs like this: /events/site/.  I'm not sure what is going on here, the site is return 404 status for these, and then they are showing up in the Webmaster Tools error report. 
URLs created by Googlebot show up as 404 errors
url;url rewriting