What is the syntax for boolean attributes, e.g. a checked checkbox, in HTML?

Question

Sounds like a bit of a silly question, but I am wondering what is the best way of stating that a checkbox is checked/unchecked in HTML.

I have seen many different examples:

<input type="checkbox" checked="checked" /> <input type="checkbox"  />  <input type="checkbox" checked="yes" /> <input type="checkbox" checked="no" />  <input type="checkbox" checked="true" /> <input type="checkbox" checked="false" /> 

Which browsers work with which ones of these, and most importantly, does jQuery figure out which box is checked in all 3?

Edit: The W3C spec seems to imply that just the checked attr being there is correct. Does that mean that checked="false" and checked="no" will still check the box though?

Answer 1

In HTML:

<input type="checkbox" checked> <input type="checkbox" checked="checked"> 

For XHTML you have to use attribute/value matching pairs:

<input type="checkbox" checked="checked" />