If you have a website and received a warning message from Google today, please take heed. Though they have sent out some mistaken messages in recent weeks, this one is for real. They are warning people that if their site blocks CSS or JS it can hurt you in the rankings. This rule has actually been pointed out by Google for a little while, but they are now getting serious about it and sending out warnings.
If you didn’t get an email today, go in to your Google search console for your site (used to be called Google Webmaster Tools) and check to see if you got the warning. You can follow the steps Google provides to get things resolved. Google has been much better at helping people through technical issues by showing what is wrong in the past year or two. If you don’t understand what to do, your web developer should.
Most importantly this is a real warning and if you get it, you should take action. Here is more on the issue from Search Engine Land.