in my html4/loose pages i always thought itw as correct specify class with an apostrophe such as class="this". I now see that minified code removes the apostrophe and leaves it as class=this. Same thing for height and width height=45 rather than height="45". If the apostrophe is not required why do we use it? it is ok to remove this and minify html site wide. perhaps it was just an old browser issue?
In certain cases, authors may specify the value of an attribute without any quotation marks. The attribute value may only contain letters (a-z and A-Z), digits (0-9), hyphens (ASCII decimal 45), periods (ASCII decimal 46), underscores (ASCII decimal 95), and colons (ASCII decimal 58). We recommend using quotation marks even when it is possible to eliminate them.
So really, I think, it's the browser that's allowing you to get away with it by parsing them when they aren't quoted. As a test, try "minifying" a page with
name='Big "Bill" Coder'
It will likely leave those quotes in.
Minifying code removes the quotes to reduce the size of the document, it adds a lot of bytes when quoted. :-) I prefer to collect savings elsewhere.