function log() { 
if (window.status.indexOf('go to') == 0) 
{ 
bug = new Image(); 
bug.src = '/tracking.aspx?R=' + document.location + '&U=' + window.status.substring(6); 
} 
} 
var elements; 
elements = document.getElementsByTagName("iframe"); 
for (var i = 0; i < elements.length; i++) { 
    if(elements[i].src.indexOf('googlesyndication.com') > -1) 
    { 
    elements[i].onfocus = log; 
    } 
    
    if(elements[i].src.indexOf('googleadservices.com') > -1) 
    { 
    elements[i].onfocus = log; 
    } 
}