var leftPos = (typeof window.screenleft == "number")?
            window.screenleft : window.screenX;

var topPos = (typeof window.screentop == "number")?
            window.screentop : window.screenY;


//IE Safai Opera Chrome 支持window.screenleft 
//Firefox 支持 window.screenX

var pageWidth = window.innerWidth,
      pageHeight = window.innerHeight;

if (typeof pageWidth != "number") {
    if(document.compatMode == "CSS1Compat") {             //判断是否处于标准模式
        pageWidth = document.documentElement.clientWidth;         
        pageHeight = document.documentElement.clientHeight;
    } else {
        pageWidth = document.body.clientWidth;            //兼容IE
        pageHeight = doucment.body.clientHeight;
    }
}