document.getElementsByClassName = function(cl) {
	var retnode = [];
	var myclass = new RegExp('\\b'+cl+'\\b');
	var elem = this.getElementsByTagName('*');
	for (var i = 0; i < elem.length; i++) {
		var classes = elem[i].className;
		if (myclass.test(classes)) retnode.push(elem[i]);
	}
	return retnode;
};

function randomBanner() {
	var banners = document.getElementsByClassName("randomBannerData");
	if(banners.length != 0) {
		var i = Math.floor(Math.random() * banners.length);
		document.getElementById("bannerImage").src = banners[i].innerHTML;
	}
}