function chooseImage() {
	var numImages = 3;
	var whichImage = Math.ceil( Math.random() * numImages );
	
	var contentElem = document.getElementById( 'content' );
	contentElem.style.background = 'url( "images/backgrounds/shot' + whichImage + '.jpg" ) no-repeat right top';
}
window.addEvent("domready", chooseImage);