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Every once in a while I get an email about W3C validation. The people emailing me either point me at the fact that my own site doesnt validate correctly (thank Facebook for most of that), or they ask me whether I think W3C Validation is important. Most of them ask even more specifically: whether I think W3C validation is important for SEO.

Since Ive taken it upon me to create articles for each question that Ive answered more than once, lets have a look at the pros and cons of W3C validation.

W3C validation & Web design

Well have a look at the pros and cons of W3C and web design first, before we dive into the SEO aspects. There are two types of validation errors in my opinion: there are errors that break or hamper rendering, which Ill refer to as hard validation errors, and there are validation errors that dont cause rendering issues, which Ill refer to as soft validation errors.

An example of a hard validation error: an unclosed anchor – – tag. This can cause serious issues. Just about any unclosed element that should be closed and is not can cause you to look at styling issues for far too long. W3C validation is a very easy way to catch coding errors like that and thus it makes debugging and continued development of HTML a lot easier.

Having hundreds of validation errors is not usually a sign of code quality, so trying to keep the number of errors, hard or soft, down is usually a good idea. Whether you really have to bring it down to zero is another discussion, as over obsessing with certain issues can be a costly thing to do. Is your client, or are you, really willing to pay to get the page to validate when all thats not working is the fact that you use an iframe (something Id call a soft validation error) when youre required to use a Strict DTD? Some clients might be willing to pay for that, most Ive worked with dont care that much.

Ive seen people do weird things to get their site to validate. Adding a JavaScript library to your site purely for the goal of getting your site to validate, for instance. Is that really a service to the websites visitors? Adding 50kb of download for each visitor because you didnt stand up to your client? I dont think so.

W3C validation & SEO

So, on to the question on a lot of peoples minds. While Googling for this subject I noticed loads of people have written about this topic, which made me decide just my own opinion wouldnt suffice for this article; so youll get mine, and the opinion of some of my friends. First of all, let me draw from my own experience.

My own opinion on Validation & SEO

Last year, while doing SEO for a major Dutch news site, I found out this site had its entire front-page show up blank in Googles cache. The reason was that they were using an unclosed – and rather obscure – HTML tag, the XMP tag. The XMP tag is basically the same as the PRE tag, but instead of rendering tags inside it, it outputs them. This XMP tag wasnt closed properly, and thus, Googles spider choked on it, causing their pages not to be indexed the way they should. So this error caused a browser, which is what Googlebot is in essence, not to render. Thats the kind of validation errors I think you should fix. For other validation errors, like the use of target=_blank with a Strict document type, I do not care, and would not want my client to spend development time on my behalf fixing it.

I do know that I use the number of errors as a sign of code quality when doing quick scans, and poor code quality can very well be a reason for ranking badly. Do remember though that validating your site with the W3C doesnt validate the semantics of your HTML.

But as I said: thats just my simple opinion, lets get some of my friends opinions:

Respected SEOs on W3C Validation

First of all I asked Aaron Wall, of SEOBook fame, his answer was pretty direct:

If you want to get links from web designers who charge high rates then W3C validation is important to SEO, otherwise it has little direct importance outside of ensuring proper rendering to end users. When one visits Amazon.comor Google or Yahoo! (or just about any billion Dollar+ internet company) they will find a website that doesn’t validate. Why is that?

Is Aaron suggesting that validation being good for SEO is a web design industry scam, because they need a better reason to get people to pay for writing valid HTML other than “we like it”? Yes, he is.

Next up was Greg Boser, his reply went along the same lines:

We try to use frameworks that validate, but we don’t spend a ton of time trying to rework a plugin or widget that cause minor errors that aren’t site operation critical.

Next up, Brent Payne, SEO Director for Tribune, seems to be right in line with my thinking:

I like to keep errors under 25 or so, though Tribune has 100+ errors. Perfect code, I don’t think is necessary but you don’t want to have too malformed of HTML. Some say it is a ranking factor, I say you just don’t want to have stuff that is too unexpected for the bots.

Dennis Goedegebuure, Senior Manager & Head of SEO at eBay Inc., said:

“It depends on the type of errors and how many, it all depends on whether the crawler can actually read the real content of the page.”

Lastly, I asked Jaimie Sirovich, the author of two technical SEO books, he said:

As long as google.com doesnt validate, Id say no. They actually don’t quote attributes, Id guess deliberately to shrink page size.

(In fact, as Dennis pointed out, Google doesn’t even close the body and html tags). When asked what kind of issues he would fix, Jaimie was very resolute:

Tag nesting, thats about it. Just make sure its a tree.

In other words: fix unclosed and or improperly nested tags, dont bother about the rest.

The verdict on W3C Validation & SEO

Most SEOs seem to agree that having code that isnt properly nested or has big errors is bad for SEO. They all agree too that its not going to get you any better rankings when you really have valid HTML.

My final conclusion thus is: both for web design & SEO reasons, youll want to fix any and all blatant errors that might cause bad rendering or parser issues. Dont worry about attributes that are not allowed though, nor about that one plugin using tags instead of . Its just not worth your time or money.