var myRand;
    
    myRand=Math.random();
    sBlBan = (myRand < 1.0/3.0);
    sBlBan2 = (myRand > 2.0/3.0);
    sOrBan = ! sBlBan && ! sBlBan2;

    if(document.layers) {
	//NN4+
	document.layers['blban'].visibility = sBlBan ? "show" : "hide";
	document.layers['blban2'].visibility = sBlBan2 ? "show" : "hide";
	document.layers['orban'].visibility = sOrBan ? "show" : "hide";
    } else if(document.getElementById) {
	//gecko(NN6) + IE 5+
	var obj = document.getElementById('blban');
	obj.style.visibility = sBlBan ? "visible" : "hidden";
	obj = document.getElementById('blban2');
	obj.style.visibility = sBlBan2 ? "visible" : "hidden";
	obj = document.getElementById('orban');
	obj.style.visibility = sOrBan ? "visible" : "hidden";
    } else if(document.all) {
	// IE 4
	document.all['blban'].style.visibility = sBlBan ? "visible" : "hidden";
	document.all['blban2'].style.visibility = sBlBan2 ? "visible" : "hidden";
	document.all['orban'].style.visibility = sOrBan ? "visible" : "hidden";
    }