function getObject(id) {
	return document.getElementById(id);
}

function findPosX(obj)
{
	var curtop = 0;
	if (obj.offsetParent)
	{
		while (obj.offsetParent)
		{
			curtop += obj.offsetLeft
			obj = obj.offsetParent;
		}
	}
	else if (obj.x)
		curtop += obj.x;
	return curtop;
}

function findPosY(obj)
{
	var curtop = 0;
	if (obj.offsetParent)
	{
		while (obj.offsetParent)
		{
			curtop += obj.offsetTop
			obj = obj.offsetParent;
		}
	}
	else if (obj.y)
		curtop += obj.y;
	return curtop;
}

var nbimage= 30;
var width;
var height;
var url;
var alte;
function banniere()
{
numimage= Math.round(Math.random()*(nbimage-1)+1);
if (numimage <= 10)
{
url = "Images/img1.jpg";
alte = "img1";
}
if (numimage > 10 && numimage <= 20)
{
url = "Images/img2.jpg";
alte = "img2";
}
if (numimage > 20)
{
url = "Images/img3.jpg";
alte = "img3";
}
getObject("banniere_home_haut").style.background = "URL(" + url + ")";
}