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What happens when you have invalid code, or attributes that mean nothing, or you have a typo in your attributes in your code? How does Google handle it? Well, Google is pretty good at crawling the whole web and the whole web often has a lot of bad code, invalid markup, typos and incorrect syntax. Google learned to crawl the imperfect web and render it properly to searchers.
John Mueller said that when you use unrecognized attributes, Google is generally able to just ignore it when they parse the HTML.
He said this on Twitter:
Unrecognized attributes are generally ignored when parsing HTML.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) August 17, 2017
So if you want to put in your attributes rel="this link rocks so much" or meta="rank this page number one" - Google will just ignore it.
Forum discussion at Twitter.
