Webmasters often use linked images, CSS, and JavaScript files in web pages to make them pretty and functional. If these resources are blocked from crawling, then Googlebot can't use them when it renders those pages for search. Google Webmaster Tools now includes a Blocked Resources Report to help you find and resolve these kinds of issues.
This report starts with the names of the hosts from which your site is using blocked resources such as JavaScript, CSS, and images. Clicking on the rows gives you the list of blocked resources and then the pages that embed them, guiding you through the steps to diagnose and resolve how we're able to crawl and index the page's content.
An update to Fetch and Render shows how these blocked resources matter. When you request a URL be fetched and rendered, it now shows screenshots rendered both as Googlebot and as a typical user. This makes it easier to recognize the issues that significantly influence why your pages are seen differently by Googlebot.
Webmaster Tools attempts to show you only the hosts that you might have influence over, so at the moment, we won't show hosts that are used by many different sites (such as popular analytics services). Because it can be time-consuming (usually not for technical reasons!) to update all robots.txt files, we recommend starting with the resources that make the most important visual difference when blocked. Our Help Center article has more information on the steps involved.
We hope this new feature makes it easier for you to spot and then unblock resources used by your website! Should you have any questions, feel free to drop by our webmaster help forums.
