Array.prototype.shuffle = function() {
var s = [];
while (this.length) s.push(this.splice(Math.random() * this.length, 1));
while (s.length) this.push(s.pop());
return this;
}

top_counter = 0;
orderArray = new Array();
for (i = 0; i <= 10; i++)
orderArray[i] = i;
orderArray.shuffle();
function refresh_top()
{
	document.getElementById("header").style.backgroundImage = "url(images/top" + orderArray[top_counter] + ".jpg)";
	top_counter++;
	if (top_counter == 11) top_counter = 0;
}

window.setInterval("refresh_top()", 30 * 1000);