You first two bullet points are correct. For the third one, there's no "skipping over" involved. The <html> and <body> opening tags are optional in HTML. The

You first two bullet points are correct. For the third one, there's no "skipping over" involved. The <html> and <body> opening tags are optional in HTML. The browser sees some non-whitespace text (the opening '{') not in the context of any other tag, auto-opens those tags, and the text starts being parsed as body text. If the page loaded slowly enough, over multiple packets that arrived separated in time, you would see the JSON text coming in and rendering as text, with all the curlies and all, until the browser gets to the <html hidden> part of the JSON. At that point, some common-error fixup dating back to the Netscape/IE 3 days kicks in: when you see an <html> or <body> tag and one has already been opened (due to some stray content at the beginning of the file, likely), you don't open a new one, but copy the attributes to the existing one. This copies the "hidden" attribute to the <html>, which hides it. After that either the script executes and does its work, per your fourth bullet point, or script is disabled and the style rule inside <noscript> unhides the <html> element, but at that point you will of course just see the JSON text, parsed as HTML. > I do however get this warning in FireFox so perhaps this is pretty fragile: I'm not sure whether the site changed since then, but now it's sending `charset=utf-8` in the content-type header, so there's no meta prescan at all. Which is what allows the emoji after "Need Help?" to be decoded correctly. Were you seeing the meta prescan warning on your local test file, or on the site itself? > I'm guessing differently-configured means not in quirks mode? No, it means things like preferences about how to handle pages without encoding declarations via various heuristics (e.g. scanning byte value frequencies and guessing what character encoding is in use based on that). Quirks mode is determined solely by the doctype of the page. This page has no doctype (since it starts with a '{'), so it's always in quirks mode. And what quirks mode does is enable a set of behaviors designed to not break content written more or less in the "before HTML 4.0" era. https://quirks.spec.whatwg.org/ https://quirks.spec.whatwg.org/ should have a more or less exhaustive list of quirks mode behaviors browsers are expected to implement. Some of these are extra-fault-tolerance (e.g. the hashless hex color and unitless length quirks), while some are just replicating pre-CSS browser rendering behavior (like the line height calculation quirk, which a bunch of sliced-image stuff relies/relied on).