defer.js

// add this as the only script before your closing body tag
// and let it load your external scripts once your DOM has finished loading.
function addJSOnload() {
    var element = document.createElement("script");
    element.src = "defer.js"; // replace your script with "defer.js"
    document.body.appendChild(element);
}
if (window.addEventListener)
    window.addEventListener("load", addJSOnload, false);
else if (window.attachEvent)
    window.attachEvent("onload", addJSOnload);
else
    window.onload = addJSOnload;