function getByClass(clsName,parent){

var oParent = parent?document.getElementById(parent):document,

eles=[],

elements=oParent.getElementsByTagName("*");

for(var i=0 l=elements.length;i<l;i++){

if(elements[i].className==clsName){

eles.push(elements[i]);

}

}

return eles;

}

window.onload = drag;

function drag(){

var oTitle = getByClass("login_logo_webqq","loginPanel")[0];

oTitle.onmousedown=fnDown;

}

function fnDown(){

var oDrag = document.getElementById("loginPanel");

document.onmousemove=function(event){

event = event || window.event;

oDrag.style.left=event.clientX+'px';

oDrag.style.top=event.clientY+'px';

}

}