Finding element with autofocus attribute doesn’t work always

[taimar]

attribute: autofocus
selector: :input[autofocus]
demo: ​http://jsfiddle.net/nk4bn/
wrong result: FF3.6, FF3.5, IE6-IE9

attribute: autofocus
selector: input[autofocus]
demo: ​http://jsfiddle.net/nk4bn/1/
wrong result: IE6, IE7

attribute: autofocus="autofocus"
selector: :input[autofocus]
demo: ​http://jsfiddle.net/nk4bn/2/
wrong result: none

attribute: autofocus="autofocus"
selector: input[autofocus]
demo: ​http://jsfiddle.net/nk4bn/3/
wrong result: none

jQuery doesn’t like/understand HTML5 boolean attributes?
​http://dev.w3.org/html5/spec/Overview.html#boolean-attribute

[timmywil]

Duplicate of #5637.