var ic = 6;
    var iso = new Array(ic);     
iso[0] = "images/headers/01.gif";
iso[1] = "images/headers/02.gif";
iso[2] = "images/headers/03.gif";
iso[3] = "images/headers/04.gif";
iso[4] = "images/headers/05.gif";
iso[5] = "images/headers/06.gif";

function pickRandom(range) {
if (Math.random)
return Math.round(Math.random() * (range-1));
else {
var now = new Date();
return (now.getTime() / 1000) % range;
}
}
var choice = pickRandom(ic);