How Important Is Valid Html Source Code For SEO?

[BarryGrant77]

continuative to the last thread ("Crufty" Web Pages ) i would start a small discussion about valid html source code and how important this issue is for SEO. I understand this as part of QS for Users, Browser, Crawler and myself. Following a few things why this is important (not most important, but a part of the whole process):

1. Website is corrently displayed to the user in most common webbrowsers
2. Webcrawler can read the source code easily
3. No errors during the crawling process
4. A clear sign for quality

I think the last point is important for the Oracle (the search engine with "G"), it can ensure quality to users.

What are your thoughts?

[torka]

According to Vanessa Fox, back when she worked for Google, Google basically discards most, if not all, of the HTML code before they ever even index a page.

(Source: http://videos.webpronews.com/2006/12...ogle-sitemaps/ She makes her comments in the course of talking about code-to-text ratio, but to my mind it doesn't really matter if we're negating the idea of code-to-text ratio or if debunking the "valid HTML" myth, either way, the bottom line is: the code gets discarded. And if the code is discarded before indexing, it can't possibly have any effect on rankings or SEO.)

Your point 2 and point 3 are pretty much the same thing. Crawlers don't actually "read" the source code in the sense of trying to parse it the way a browser would. They simply collect what they find and carry it back, intact, to Google for further processing. Since they aren't trying to read the code, the only issue is if there is some kind of error condition that prevents them from retrieving all the page source.

And since the spiders are written to be very forgiving, it would have to be some abysmally bad code indeed before it would be enough to stop one of those little guys.

Any code that messed up would almost certainly be unparsable by current browser software, and so would not display correctly for human visitors, either.

And I totally agree that code that messed up is not a sign of a good quality site. Especially if the code stays that messed up long enough for the spiders to find it in that condition more than once.

So, yeah, if a site's HTML is so FUBAR the spiders can't retrieve all the source, and browsers can't render it, then I would say visiting that site isn't going to be a good visitor experience, and Google and the others would be totally justified in ranking such a site very low (or excluding it from their results entirely).

But just because code can be parsed and rendered by a browser, this doesn't mean it's "valid." There are loads of "invalid" websites that still display perfectly well across a whole range of browsers, and are perfectly spiderable.

And the question is whether "valid HTML" makes a difference for SEO.

My answer to that is, IMO, no. I've seen no evidence that validation is even checked by the SE's, much less that it's used as a ranking factor.

Anyone who doubts this just needs to run a validator against the top-ranking websites for most search queries.

(According to the W3C validator, Google's own home page throws up 65 errors and 8 warnings. It would be very odd for them to insist on "valid HTML" from others when they don't seem to see the need for it on their own home page.)

My

--Torka

[ktaylor310]

It's my understanding that validation is important because it helps weed out cross-browser problems and can help prevent problems in the future as browsers & code continue to evolve. I don't believe it has any value as far as ranking goes and I don't think Google takes it as a mark of quality.

That said, I have bid on web designs before wherein someone within the company had html experience, checked out the code on my website, and commented that my code was very clean. So in a situation like that it could be taken as a mark of quality, but I think that is rare.

I always validate my pages before publishing because it helps me to quickly find errors. There are some things that take way too much time to validate though, like embedding a flash file. If it is something minor, I don't lose any sleep over that part of the code not validating.

In Mr. Lansik's words:

we do not penalize or treat differently those pages whose HTML won't validate very nicely

[Bromoney]

It's something you should do, but ultimately not that important for SEO

[Sporkman]

I run the validator to find actual mistakes (like forgetting to close a tag) which aren't apparent by looking the rendered page in the browser. I won't go out of my way to dot every 'i' though (like addressing all the complaints re missing ALT tags).

Plus the adsense blurbs always invoke errors in the validator.

[ktaylor310]

I agree! There are times you don't want alt text popping up, like when it appears on top of your navigation link or when it is associated with a background image. Truthfully, most of your clients could care less if your code is spotless. They want to know their site is performing without issues, but they do not want to pay for the extra time associated with finding away to validate every piece of code.

<------ love the banana!

[SashaMike]

Its all about best practices but not mandatory ones. W3C validation is not a validation made for SEARCH ENGINES only. Having a proper website is crucial for everything.

Everyone knows HTML is a loosely typed language. If you leave a tag open, doesn't matter. But if you close it, you create a clean website.

Again, its about best practice!

[rosesmith]

I’ve always understood web standards to be good for SEO because they improve crawlability, remove extraneous code and make the page easier to index.

Plus, I remember reading somewhere that this tied into Google’s mission to make the world’s information accessible to all.

However, I find it hard to believe that search engine spiders haven’t evolved to the point where they can ignore the odd un-nested tag or a bit of invalid code. The spiders are (literally) at the forefront of search - it’s hard to believe search engines don’t spend as much time developing them as they do their algorithims.