For the second day in a row, Matt Cutts answers a question from a fellow Googler in a Webmaster Help video. This one comes from Webmaster Trends analyst John Mueller:
“Googlebot keeps crawling my JavaScript and thinking that text in my scripts refers to URLs. Can I just disallow crawling of my JavaScript files to fix that.”
Long story short, he wouldn’t advise it. If there’s one individual JavaScript file that’s the source of the problem, you could disallow that, he says.
Also, don’t block CSS.
He says, “It turns out, as we’re executing JavaScript, we do look at the attributes, so you can actually use JavaScript, and put like a nofollow attribute on individual URLs, and so it is the sort of thing where you can do link level granularity there. And you can block, for example, and individual JavaScript file, but in general, I would not recommend blocking all of your JavaScript files.”
Cutts has talked about blocking Google from crawling JavaScript, and how it can hurt your rankings, in the past. Watch that video here.