function chooseBg() {
	var randombgs=["/fileadmin/templates/img/content/banner1_bg_1.jpg", "/fileadmin/templates/img/content/banner1_bg_2.jpg", "/fileadmin/templates/img/content/banner1_bg_3.jpg"];
	document.getElementById('banner1').style.backgroundImage='url('+randombgs[Math.floor(Math.random()*randombgs.length)]+')';
}