Google's Warning You About Blocked JavaScript and CSS

Webmasters have begun receiving alerts from Google notifying them that their sites are blocking vital CSS and JavaScript files. The alerts are coming in the form of a message within the Google Search Console (formerly Google Webmaster Tools) as well as a detailed email message like the one shown below.

These alerts came in mass making some believe they were false positives. However, after a little investigation many of the initial 'false positives' were the result of a site's CMS blocking the include folder by default. As you may already know, include folders contain your site's CSS and JS.

If you've received this warning, follow the steps outlined in the notification (use Fetch as Google) to help determine how badly your site may be affected and fix any issues. As a follow-up, Google is also recommending that you add the following to your robots.txt file:

User-Agent: Googlebot Allow: .js Allow: .css

You should also double check to be sure you're not missing anything by checking out the Blocked Resources section within the Google Search Console. Once you've unblocked the resources, you can wait to let Googlebot do its work or resubmit your URL.