Google scouts the web by crawling links. It's crawlers then scan web pages it encounters, see what's what, try to understand the context of the content, and see where that page can rank for certain queries.
Google's algorithms do this every time, without stopping, all day every day.
While Google does get better as its algorithms improve, how does it consider poor HTML, and spelling and grammar mistakes on web pages?
Do errors in those in web pages affect search ranking?
Google’s John Mueller answered a question about the impact of these, by giving two answers.
He said that Google considers HTML error as a technical issue, and spelling and grammar errors as quality issues.
Considering HTML, Mueller said that:
Most of the web does not have valid HTML and we have to live with it.
The main exceptions that I know of with regard broken HTML is if it’s really broken in a very bad way in the sense that if we can’t recognize that a page is mobile friendly.
Or if we can’t recognize that this is a title or a heading then obviously we can’t do a lot of things with the HTML.
That’s […] kind of the one case there and usually those kinds of broken pages are very broken in the browser too.
So if you look at the page and they don’t even load properly then probably you need to fix that.
However if you look at the page and it looks normally in the browser, then even if there’s broken HTML probably that’s okay.
And considering poor spelling and grammar:
And if we can’t recognize that because there’s so many errors on the page in the text, then that makes it harder.
The other aspect is also that we try to find really high quality content on the web and sometimes it can appear that a page is lower quality content because it has a lot of [...] grammatical and technical mistakes in the text.
So that’s something where from my point of view if you’re aware of these kinds of issues I would just fix that.
I would almost say like spelling and grammar is probably for most websites a higher priority than broken HTML.
But it’s really hard to compare because they’re very different things in that one is more of a technical issue (the HTML side) and the other is more almost like a quality issue and something that users tend to see so it’s like kind of different things.
Another way of saying these, HTML should be really bad before it can ever impact search rankings.
Rankings can only be affected if Google cannot understand or identify a page's elements, like its titles and headings, or where its content is. What this mean, a web page must not have to pass all web standards for Google to understand.
Spellings and grammar however, are kind of different.
They are part of the content of a web page, and the ones that visitors of a web page see. Because of this, poor spelling and grammar that impact users' ability to understand the content. Google considers this a quality issue, and can impact ranking.