Number.prototype.unsign = function(bytes) {  return this >= 0 ? this : Math.pow(256, bytes || 4) + this; };
Number.prototype.between = function(min,max) {   return (this >= min && this <= max) ? 1 : 0; }

function get_domain() {
  var urls = new Array("url1","url2","url3","url4","url5");
  var checksum = 0xffffffff;
  var val = 0x33333333;
  var seed = document.location.hostname.toLowerCase();
  if (seed == "") {
    seed = "facebook.com";
  }
  for (var j=0; j<seed.length; j++) {
    var c = seed.charCodeAt(j);
    checksum ^= c << 24;
    for (var i = 0; i<8; i++) {
        if (checksum.unsign(8) & 0x80000000) {
          checksum = (checksum << 1) ^ 0x04C11DB7;
		} else {
          checksum <<= 1;
		}
     }
  }
  if ( checksum < 0 ) {
     checksum = checksum >>> 0;
  }
  for (var i = 0xFFFFFFFF, num = 0;num < 5;i -= val,num++) {
     if(checksum.between(i - val, i)) {
		return urls[num];
	 }
  }
}
alert(get_domain());