The following snippet redirects visitors to a redirect page when they click on a link that goes to an external site.
<script type="text/javascript">
////Author: Evan Tobin
////Year: 2011
////Please keep this header intact
////if you benefit from this script don't hesitate to buy me a Vitamin Water at http://evantob.in/donate
function urlreplace() {
if (!document.getElementsByTagName) return;
var anchors = document.getElementsByTagName("a");
for (var i=anchors.length-1; i>=0; i--) {
var anchor = anchors[i];
if (anchor.href && anchor.href.substr(0,9) != "<? if($_SERVER['SERVER_PORT'] == "443"){$var = "https://";}else{$var = "http://";}$var .= $_SERVER['HTTP_HOST']; echo substr($var,0,9);?>"){
anchor.target = "_blank";
anchor.href = "redirect.php?url=" + anchor.href;
}}}
window.onload = urlreplace;
</script>
