is it autofocus=“autofocus” or autofocus?

Question

I seem to recall most (maybe all) attributes in previously versions of HTML (before HTML5) required attributes to have values, like readonly=\"readonly\".

Answer 1

No, it's enough to specify the attribute itself. It was that way also in HTML 4.

A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.

If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.

Example:

 Cheese