Defer-javascript

<script type="text/javascript">
    function downloadJSAtOnload() {
        var element = document.createElement("script");
        element.src = "!!!YOURJAVASCRIPTHERE!!!.js";
        document.body.appendChild(element);
    }
    if (window.addEventListener)
        window.addEventListener("load", downloadJSAtOnload, false);
    else if (window.attachEvent)
        window.attachEvent("onload", downloadJSAtOnload);
    else 
        window.onload = downloadJSAtOnload;
</script>