Interestingly, they are using a custom random function
today=new Date();
jran=today.getTime();
var number=5;
var random_number=1;
var bgsnd="/games/random/bgsnd.wav";
var images="/games/random/intro.JPG";
var sizes=" width=602 height=228";
function randomizeNumber()
{
ia=9301;
ic=49297;
im=233280;
jran = (jran*ia+ic) % im;
random_number=Math.ceil( (jran/(im*1.0)) *number);
if (random_number==1){
bgsnd="audio/intro/yeeha.wav";}
if (random_number==2){
bgsnd="audio/intro/crash_10.wav";}
if (random_number==3){
bgsnd="audio/intro/heybuddy.wav";}
if (random_number==4){
bgsnd="audio/intro/lovethatmud.wav";}
if (random_number==5){
bgsnd="audio/intro/webintro.wav";}
}
And then they run it when the page opens randomizeNumber();
document.open();
if (version == "n3" || version == "n4"){
document.write("");}
if (version == "e3" || version == "e4"){
document.write("");}
document.close();