I found this thread while looking for a solution to this problem. Here is what I've come up with so far. No need to screw around with your link tags -- just add the image tag in your document to direct log data to the PHP script (or whatever). Works with Explorer 6 and Firefox, untested with other browsers.
<html>
<head>
<script>
document.onclick = exitURL; // route all click events
function exitURL(e) {
if (!document.getElementById) return true; // DOM only
var eTag = document.getElementById('tracker');
var uLog = '/path/to/logscript.php?url=';
var isLink = false;
if (!e) {
var e = window.event; // IE
var elmClick = e.srcElement;
} else {
var elmClick = e.target; // FF
}
while (String(elmClick.nodeName) != "A") {
elmClick=elmClick.parentNode; // up the tree
if (String(elmClick.nodeName) == "HTML") return true;
}
url = String(elmClick);
if (url.indexOf("http") != -1 && url.indexOf(location.hostname) == -1) {
eTag.onerror = function() { document.location.href = url; }
eTag.src = uLog + url;
return false; // wait for log, then leave page
}
return true; // pass back to originating object
}
</script>
</head>
<body>
<a href='http://www.example.com'>Example</a>
<img id='tracker' width=0 height=0 border=0>
</body>
</html>
All click events are routed through this function, which checks to make sure it's an anchor tag. The indexOf checks for http (non-local) links on different hostnames. The onerror event fires when the image fails to load (because it's not really an image), which then directs the browser to the requested page. Should fail cleanly on browsers that don't support it.