var x = 50,y = 60;
var xin = true,yin = true;
var step = 1;
var delay = 20;
var obj = document.getelementbyid("codefans_net") ;

function float() {
    var l = t = 0;
    var r = document.documentelement.clientwidth - obj.offsetwidth;
    var b = document.documentelement.clientheight - obj.offsetheight;
	obj.style.left = x + document.documentelement.scrollleft + "px";
    obj.style.top = y + document.documentelement.scrolltop + "px";
    obj.style.zindex="9999"; 
    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
    }
}
var itl = setinterval("float()", delay);

obj.onmouseover = function() {
    clearinterval(itl);
}
obj.onmouseout = function() {
    itl = setinterval("float()", delay);
}