//Edit this line to list all of your background images
var backgroundSrcs = new Array("../images/contentheader1.jpg","../images/contentheader2.jpg","../images/contentheader3.jpg","../images/contentheader4.jpg","../images/contentheader5.jpg","../images/contentheader6.jpg","../images/contentheader7.jpg","../images/contentheader8.jpg","../images/contentheader9.jpg","../images/contentheader10.jpg","../images/contentheader11.jpg","../images/contentheader12.jpg")

function pickimage(){
//This line picks an image at random from the list you entered above
var bgimage=backgroundSrcs[(Math.round(Math.random()*(backgroundSrcs.length-1)))]

//This line applies the background image to your masthead
document.getElementById("content-header").style.background = "url('" + bgimage + "')";
}