var x = 0, y = 0;
var xin = true, yin = true;
var step = 1;
var delay = 30;
var floatad = document.getElementById("floatad");
var itl = setInterval("floatAD()", delay);
function floatAD() {
	var L = 0, T = 0;
	//var R = document.body.clientWidth-floatad.offsetWidth;
	//var B = document.body.clientHeight-floatad.offsetHeight;
        var R = window.screen.width-floatad.offsetWidth;
	var B = window.screen.height-floatad.offsetHeight;

	floatad.style.left = x + document.body.scrollLeft;
	floatad.style.top = y + document.body.scrollTop;
	x = x + step*(xin?1:-1);
	if (x < L) { xin = true; x = L; }
	if (x > R) { xin = false; x = R; }
	y = y + step*(yin?1:-1);
	if (y < T) { yin = true; y = T; }
	if (y > B) { yin = false; y = B; }
}

//floatad.onmouseover = function() { clearInterval(itl) }
//floatad.onmouseout = function() { itl=setInterval("floatAD()", delay) }