function changeHeader() { var Header=new Array("testimonial-container1", "testimonial-container2","testimonial-container3","testimonial-container4","testimonial-container5","testimonial-container6","testimonial-container7","testimonial-container8","testimonial-container9","testimonial-container10","testimonial-container11"); var l = Header.length; var rnd_no = Math.floor(l*Math.random()); document.getElementById(Header[rnd_no]).style.display="block"; }