function addEventToObject(obj, evt, func) {
	var oldhandler = obj[evt];
	obj[evt] = (typeof obj[evt] != 'function') ? func : function(){oldhandler();func();};
}

function aleatoire() {
	if (!document.getElementById) return;
	image = new Array();
	image[1] = "cover/cover1.jpg";
	image[2] = "cover/cover2.jpg";
	image[3] = "cover/cover3.jpg";
	image[4] = "cover/cover4.jpg";
	var realenght = image.length-1;
	var x = Math.round(Math.random()*realenght);
	if (x < 1) {
		x = 1;
	}
	if (x > realenght) {
		x = realenght;
	}
	document.getElementById('splash').style.backgroundImage = "url("+image[x]+")";
}

addEventToObject(window,'onload',aleatoire);