Matt Cutts said it will make for a better crawl and give Google get a better idea of what is going on with your site and return better results to the user. Here is the video:
Here is the transcript of this video:
0:02 Hi everybody.
0:03 Matt Cutts here.
0:04 I just have a short public service announcement rather
0:07 than a question today.
0:08 And the PSA is this.
0:15 please take a few minutes and just take that out of the
0:20 CSS, and get a better idea of what's going on on the page.
0:24 A lot of people block it because they think, this is
0:26 going to be resources that I don't want to have the
0:29 bandwidth or something.
0:30 But Googlebot is pretty smart about not crawling stuff too
0:33 fast. And a lot of people will do things like, they'll check
0:45 And so we're not able to crawl the site as effectively as we
0:48 would like.
0:49 In addition, Google is getting better at processing
0:52 It's getting better at things like looking at CSS to figure
0:55 out what's important on the page.
0:58 So if you do block Googlebot, I would ask, please take a
1:01 little bit of time, go ahead and remove those blocks from
1:03 the robots.txt, so you can let Googlebot in, get a better
1:06 idea of what's going on with your site, get a better idea
1:09 of what's going on with your page.
1:10 And then that just helps everybody, in terms of if we
1:13 can find the best search results, we'll be able to
1:15 return them higher to users.
1:16 So thanks if you can take the chance.
1:18 I know it's kind of a common idiom for people to just say,
1:23 But you don't need to do that now.
1:25 So please, in fact, actively let Googlebot crawl things
Personally, I rarely block these files from Google or anyone else.
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