On some links on my HTML page I have a special CSS class, that when clicked, I make a ajax call to a click.aspx page and track the click.
<a href="..." class="click" id="blah-1">blah-1</a>
$(".click").bind("click", function() {
$.get("/click.aspx?&source=" + $(this).attr("id"));
});
So what is happening is the value of source, after clicking a few links (that open in a new window) becomes:
source=blah1
then it becomes
source=blah1,blah2