when reading an article, there is a link to a W3C document, mainly about the process of browser parsing HTML. Because the browser has a fault-tolerant mechanism, even tags written outside < / html > will be parsed into the < body > tag, but as far as I understand it, there is no clear indication in the document how to parse the content outside the < html > tag, except for the paragraph 8.2.5.5 . But since it is not clear what the foreign content means here, it is not sure whether this paragraph is a rule for parsing content outside the < html > tag. I hope the bosses will guide us.