Google announced they have expanded the Site Error reporting within Google Webmaster Tools.
Now the reports show breakdowns of the errors over the past 90 days by error type.
Google has broken down each category; DNS, server connectivity, and robots.txt fetch; into more specific errors to provide you with a better analysis of your site's health. Now site errors will display statistics for each of your site-wide crawl errors from the past 90 days. It will also show the failure rates for any category-specific errors that have been affecting your site.
Here is a screen shot:

This tool is becoming more and more essential to webmasters every day.
Forum discussion at WebmasterWorld.

Comments:
Joshua
08/30/2012 07:48 pm
i not care, anyway it not informative. last time google have lot of dns errors, sites up, everything work well, but them have errors. also most of their 404 errors is not real. some sites linking us using broken links, also google love to index search results of other search engines.
Scot Small
08/30/2012 10:28 pm
Why are you advertising link buying on your site? PR4- PR8 Is this not what Google is going after with the newest updates?