swa66 - 12:36 am on Feb 23, 2013 (gmt 0)
In all html (also in xhtml5) except for HTML5 you *have* to encode a content &.
HTML5 allows the author to write worse code than it needs to allow. So you can get away with it in that standard provided the characters following the & do not look like an htmlentity - and since HTML5 is now a "living" standard: you do not know what html entities they will invent in the future. So you cannot guarantee that in the future it will not start to "look like" an htmlentity.
A useless thing for lazy authors IMHO. - But HTML5 is stuffed with that kind of thing.
So not encoding every content & in an html document as & is a mistake IMHO - of equal proportion to using < or > in the content that's not encoded as < or > .
Regardless of standards, browsers can recover from the error in many cases but let's assume you write:
It's an error, but which did you intend
<a href="http://www.example.com/file?a=1©=2"> (insert a copyright sign, that's missing the semicolon ?)
<a href="http://www.example.com/file?a=1&copy=2"> (an unescaped ampersand?)
Validators hopefully will continue to flag it as errors.