Unfortunately an ajax request gets the entire file, but you can filter the content once it's retrieved:
$.ajax({
url:href,
type:'GET',
success: function(data) {
var content = $('<div>').append(data).find('#content');
$('#content').html( content );
}
});
Note the use of a dummy element as find() only works with descendants, and won't find root elements.
or let jQuery filter it for you:
$('#content').load(href + ' #IDofDivToFind');
I'm assuming this isn't a cross domain request, as that won't work, only pages on the same domain.