var twurl = "tvitvi.com/twit.php";
//  var twurl = "mikroakademiet.com/twit.php";
//  var twurl = "www.nelsondigital.com/jon/twit.php";

var str ='<iframe style="width:371px; height:107px; ';
    str+='padding:0; margin:0; overflow:hidden;" ';
    str+='frameborder="0" scrolling="no" ';
    str+='src="http://' + twurl + '"></iframe>';
    document.write(str);