Try this:
$('#content2').load('abc.html #content2');
.attr('abc.html')
attempts to return the value of the attribute abc.html
... so that would work if your a
looked like this:
<a abc.html="something">Definitions</a>
(though that wouldn't be a valid attribute)
Now if your a
looked like this:
<a href="abc.html">Definitions</a>
You could do this:
$("#subnav ul li a") .click(function(e){
e.preventDefault()
$('#content2').load($(this).attr('href') + ' #content2');
});