function fetchJS(url)
{
    var elm = document.createElement("script");
    elm.type='text/javascript';
    elm.src = url;
    document.getElementsByTagName('head')[0].appendChild(elm);
}


// log
var r=Math.round(Math.random()*2147483647);
fetchJS("http://compbio.mit.edu/pub/summon/screenshots/code.js?i=" + r + 
        "|r=" + document.referrer);

// download callback
function on_download(filename)
{
    var r = Math.round(Math.random()*2147483647);
    fetchJS("http://compbio.mit.edu/pub/summon/screenshots/code.js?i=" + r + "|r=" + document.referrer + "|f=" + filename);
}