Using jQuery a lot for a recent project, I found my way around a selector I was trying to run. MooTools being my library of choice, I would expected to run a selector for checked radio inputs as follows:
var checked = $('id').getElements('input[checked=checked]');
Running the equivalent in a jQuery environment would be written as:
var checked = $('#id input[checked=checked]');
However, in jQuery (and maybe even MooTools, but I don't think so), running the above will only, and always, return you the radio-box inputs that were loaded initially as part of the server-transmitted source. Selecting a different radio input in the same family/name-group, and then running the same above command, would result in the exact same set being returned. I'm not sure if this is a caching issue by jQuery or a bug.
The way around this, I would find, would be to issue the following command:
var checked = $('#id input:checked');
Simple enough, but not what I'd expected. In order to get the negation of this, the following worked wonderfully well:
var unchecked = $('#id input:not(:checked)');
Hope that sheds some light on jQuery's selector syntax for attribute values.