Do you know a public search engine which allows search on HTML tags?
The usage will be to search websites with HTML5 tags such as
<canvas> being able to search over the class names could also be useful.
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There once was a website from Google. Sadly this doesn't work anymore! Maybe you could contact them?
You could also try to search in this website.
I also found on Google this but this is not free, as I could see.
Otherwise, I don't know a tool that can lookup/search HTML tags! I also don't know anyone, even I know a lot of web developers!