Google says Blocking CSS or Javascript files may have a negative impact on your SEO

Back in October 2014, Google updated their Webmaster Guidelines to say that blocking CSS or Javascript files may have a negative impact on SEO. Sending out warning messages now seems to make that more significant really. So what are Google trying to do here? Are they just trying to better understand the positioning and prominence of page content?

That was the fourth topic on the most recent TWIO episode, and here’s what our guests had to say about it…

KEVIN GIBBONS: It’s interesting ‘cause Google wants to, in some ways, know it all, but they want to have as much information as they can about any webpage and I think one of the things… I went to MozCon two or three weeks ago and it’s interesting ‘cause we were looking at the future of search and where Google are heading, not just where they are now, and looking ahead obviously some of this is working now but it’s more early phases, they’re trying to make sure that everything is about user experience. And that means knowing everything about the CSS and Javascript, they can more accurately understand what’s happening on that webpage, they can make sure that they understand where everything’s positioned for a starting point, but now it’s probably taking it further. The more they know about how users are likely to engage with that page better because they can understand the intent behind, which search results to serve.

I’ve started to notice quite interestingly things like they’ve started to put, if you ask a question to Google, they have a dropdown. Has anyone had this? A dropdown of questions underneath. I’ve only noticed it for the first time this week, and had a sort of selection of choices. I’ll tweet it up. I’m not sure I’ve seen anyone else share that before. It looked quite interesting.

DAVID BAIN: Yeah, it sounds interesting. I haven’t seen that.

KEVIN GIBBONS: But no, it’s just interesting because they’re trying to with the whole user experience approach, obviously make it about how people engage with that page. And if you bounce back out of the website after seeing a page which looks like it’s well optimised, that’s not a good user experience. So the more they can read into the design and the reaction that people are likely to have, alongside that they have obviously from Chrome, from their point of view, you can bounce back out of a query very quickly, so that’s not a good user experience. Yeah, I don’t know. It’s the more data the better the decisions they can make, so I can see why they’re trying to do that.

It’s a bit like the mobile update where perhaps it hasn’t been rolled-out and used as heavily as it will be in the future, but if they can start collecting data and forcing people into behaviour that they think good website should look like, then that’s giving people a push in the right direction I guess right now.

DAVID BAIN: Yeah, you can kind of understand it because with CSS and Javascript you can make some significant manipulations to how a page looks. It used to be in the past that you could just do simple things like use certain heading numbers or perhaps bring in different inline styles but you’d see everything within the source code. But now you’ve got more and more elements that impact how a page looks that happens off the page directly. So if Google isn’t aware of that, then perhaps a piece of content that’s prominent in the source code, because of styling for whatever reason, looks really small and is quite low down within the main body content…

KEVIN GIBBONS: We’ve had a client that used tabs within their page, so it’s a good way for them to have all of their company on one single url and from that perspective it’s a good user experience, ‘cause rather than dumping all of the content onto one page it’s easy for them to click through without having to reload page. And Google last year was probably ranking that content very favourably. This year it’s not doing as well and we’re internally advising again to make sure that you definitely want to have the right user experience. You need to pay attention to what Google views as the right experience as well, that it’s having that balance, basically.

DAVID BAIN: Alex, I saw you nodding away to part of that. Which part of that did you agree with?

ALEX TUCKER: Yeah, I really agree. I think Google’s trying to be quite smart about experiencing a website as a user would, which means they need to understand the CSS and Javascript and everything else that goes into a page and a site and I kind of wonder why you would hide it as well. But yeah, I completely agree with Kevin that Google’s just very focused on delivering relevant and good user experience to users.

DAVID BAIN: Yeah, that’s right. It’s likely to be spammers, people that are trying to deliver a different version of a webpage to users and search engines that should be most concerned about this kind of thing. Emily, what are your thoughts on this? Do you focus on producing written content for a webpage without being involved within the styling and code behind that or do you have influence regarding the code as well?

EMILY HILL: I’m certainly no coder but I do try to talk to people who do know about code and do know about design because you have to try to marry up the copy with the visual look – it wouldn’t make any sense to separate the two completely, so you have to understand its context. I’m not sure that I can really add to what Alex and Kevin have said about it actually. I think they’ve covered it extremely well. I mean, ever since the Hummingbird update a couple of years ago, Google’s been crystal clear that its key interest is in understanding how users experience websites and their content and their design and how engaged they are with what we’re providing to them, so it seems like a perfectly logical step in that progression.

DAVID BAIN: Absolutely. And Pete, I presume that this is something you would agree with as well, that Google was probably trying to do the right things, see things more from a user perspective and that the only people that should be concerned about this are people that are trying to manipulate Google’s results?

PETE CAMPBELL: Yes and no. I mean, there certainly is the point that Google do use Javascript to, like, click, show a paragraph and you show more. But I guess, I used to recommend sometimes to block Javascript to clients because of spider traps. You know, if you get large ecommerce websites with 50,000 urls, you know, and we’ve seen this just recently. We had a client, new client, for whatever reason they were referring 50 different CSS style sheets, which can cause a lot of extra weight, and back until recently in the last year or so, Google didn’t actually have the ability to render CSS and Javascript, so they didn’t see webpages as a human, they just saw the HMTL code. Whereas now (and you can test this yourself within the Webmaster search console) you can actually now see the pages as Google sees them, where it shows its full render. So I guess it’s kind of gone the other way. It used to be in my mind a good thing to look to block some of those resources because it would result in Google indexing your site better. But there are certainly cases now, as especially as more people use things like Javascript to code more interactive experiences, where unless Google has access to that code, then they can’t see all the source code that’s on the site. So yeah, it is about matching user experience but to my opinion there was a time where possibly looking to block CSS and Javascript was not a bad idea.

DAVID BAIN: And do you think that it will ever go back to the stage where it’s actually better having all styling elements and Javascript within the same page because speed happens fairly quickly? Or do you think it’s going to always be the case where things like CSS are on another page and having to be accessed from that page?

PETE CAMPBELL: I think there’ll always be better as external resources. Since you have a library and you download it once, that’s cached in your browser and then the browser interface can refer to that again and again. And particularly with the introduction of things like HTTP/2, where the way in internet over the next few years will work is that the browser will grab everything at once, whereas at the moment if you want to go on a webpage it works a bit like, you know, slowly ordering a pizza. You have to say, ‘I would like pepperoni, I would like pineapple.’ Whereas the way the internet is going is it’s going to grab everything at once. So I think external files are going to be even more important.

Here’s where you can watch the reply of the show that features this discussionThis Week In Organic is the weekly show that debates the ramifications of the latest SEO and content marketing news. Sign-up to watch the next live show at

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