The problem is that you are passing the result of a function, not a function.
I.e. do this instead
$(function(){
$('a.navlink').click(function(e){
e.preventDefault();
var linkLocation = $(this).attr('href');
$('#main-content').fadeOut(1500, function(){
document.location.href = linkLocation;
});
});
});
A good explanation of jQuery callbacks:
http://learn.jquery.com/about-jquery/how-jquery-works/#callbacks-and-functions