function alertinfo(id){//显示弹出层
var obj = document.getElementById(id);
var W = screen.width;//取得屏幕分辨率宽度
var H = screen.height;//取得屏幕分辨率高度
var yScroll;//取滚动条高度
if (self.pageYOffset) {
yScroll = self.pageYOffset;
} else if (document.documentElement && document.documentElement.scrollTop){
yScroll = document.documentElement.scrollTop;
} else if (document.body) {
yScroll = document.body.scrollTop;
}

//obj.style.marginLeft= (W/2 - 200) + "px";
obj.style.top= (H/2 -90 - 125　+　yScroll) + "px";
document.getElementById("bg").style.display="block";
obj.style.display="block";

var scrollstyle = scrolls();
scrollstyle.style.overflowX = "hidden";
scrollstyle.style.overflowY = "hidden";
}
function closediv(id){//关闭弹出层
document.getElementById(id).style.display="none";
document.getElementById("bg").style.display="none";

var scrollstyle = scrolls();
scrollstyle.style.overflowY = "auto";
scrollstyle.style.overflowX = "hidden";
}
function scrolls(){//取浏览器类型
var temp_h1 = document.body.clientHeight;
var temp_h2 = document.documentElement.clientHeight;
var isXhtml = (temp_h2<=temp_h1&&temp_h2!=0)?true:false;
var htmlbody = isXhtml?document.documentElement:document.body;
return htmlbody;
}