var classes = ["top_bg01", "top_bg02", "top_bg03", "top_bg04", "top_bg05", "top_bg06", "top_bg07", "top_bg08", "top_bg09", "top_bg10"];
var period = 15000; //msec
var contentWrapperElement = null;

function GetHtmlElement(name)
{
	var element;

	element = document.getElementById(name);
	if (element == null)
		element = document.getElementsByName(name)[0];
	else if (element == null)
		element = document.all[name];

	return element;
}

var onBgTimer = function ()
{
	var i = Math.floor(Math.random() * 9);

	window.contentWrapperElement.className = "contentWrapper " + classes[i];
	setTimeout(onBgTimer, period)
}