single line comment in HTML

Question

Is there a way to comment out a single line in HTML using just an escape sequence at the start of the line? Similar to using # or // in other languages

Answer 1

TL;DR For conforming browsers, yes; but there are no conforming browsers, so no.

According to the HTML 4 specification, hello--> is a perfectly valid comment. However, I've not found a browser which implements this correctly (i.e. per the specification) due to developers not knowing, nor following, the standards (as digitaldreamer pointed out).

You can find the definition of a comment for HTML4 on the w3c's website: http://www.w3.org/TR/html4/intro/sgmltut.html#h-3.2.4

Another thing that many browsers get wrong is that -- > closes a comment just like -->.