window.onload = EnteteRandom;
function EnteteRandom() {
var randomNum;
var picCount = 7;
randomNum =  Math.floor(Math.random()*picCount)+1;
var mySrc="actifs/images/entete/pic"+randomNum+".jpg"
var myImgEl = document.createElement("img");
myImgEl.setAttribute("src",mySrc);
var theDiv = document.getElementById("entete").style.background="url("+mySrc+")";
theDiv.appendChild(myImgEl);
}