function change_bgr(name){
	elem = document.getElementsByClassName('content_div');
	for (var i=0; i<elem.length; i++){
		elem[i].id=name;
	}
}


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;
};