function ChangeCSSBgImg() {
	if (!document.getElementById) return false;

	var MyElement = "header" //The ID of the element you want to change
	var ImgPath = "images/header/" //The file path to your images

	if (!document.getElementById(MyElement)) return false;

	var random_images = new Array ();

	random_images[0] = "header_7.jpg";

	var $header = document.getElementById(MyElement);
	var $backgroundurl = $header.style.backgroundImage;
	var ImgURL = "url(" + ImgPath + random_images[rand(random_images.length)] + ")";

	if ($backgroundurl != ImgURL) {
		$header.style.backgroundImage = ImgURL;
	}

	movement = setTimeout("ChangeCSSBgImg()",9999960000);
}

/* random number generator */
function rand(n) {
  return ( Math.floor ( Math.random ( ) * n ) );
}

/* Custom onload function */
function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}
/* trigger onload */
addLoadEvent(ChangeCSSBgImg);