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 str_login = '<form method=post action=login.asp target=alogin><div id="login"><div id=logintitle>用户登陆 <a href="javascript:close();">关闭</a> </div><div id=loginpanel>用户名：<input type=text name=u1 value=用户名 onclick=this.value=\"\";> <br>密　码：<input type=password name=p1 value=请输入登录密码 onclick=this.value=\"\";> <br><input type=submit value=登录 class=btn1 style=width:40px;margin-left:48px;> <a href=register.asp>免费注册</a></div> </div><iframe name=alogin width=0 height=0></iframe></form>';

document.write(str_login);

function M(id){
    return document.getElementById(id);//用M()方法代替document.getElementById(id)
}
function MC(t){
   return document.createElement(t);//用MC()方法代替document.createElement(t)
};
//判断浏览器是否为IE
function isIE(){
      return (document.all && window.ActiveXObject && !window.opera) ? true : false;
} 
//取得页面的高宽
function getBodySize(){
   var bodySize = [];
   with(document.body) {
    bodySize[0] = (scrollWidth>clientWidth)?scrollWidth:clientWidth;//如果滚动条的宽度大于页面的宽度，取得滚动条的宽度，否则取页面宽度
    bodySize[1] = (scrollHeight>clientHeight)?scrollHeight:clientHeight;//如果滚动条的高度大于页面的高度，取得滚动条的高度，否则取高度
   }
   return bodySize;
}
//创建遮盖层
function popCoverDiv(){
   if (M("cover_div")) {
   //如果存在遮盖层，则让其显示 
    M("cover_div").style.display = 'block';
   } else {
   //否则创建遮盖层
    var coverDiv = MC('div');
    document.body.appendChild(coverDiv);
    coverDiv.id = 'cover_div';
    with(coverDiv.style) {
     position = 'absolute';
     background = '#CCCCCC';
     left = '0px';
     top = '0px';
     var bodySize = getBodySize();
     width = bodySize[0] + 'px'
     height = bodySize[1] + 'px';
	 zIndex = 1;
     if (isIE()) {
      filter = "Alpha(Opacity=60)";//IE逆境
     } else {
      opacity = 0.6;
     }
    }
   }
}

 
//让登陆层显示为块 
function showLogin() {
	var login=M("login");
	var bodySize = getBodySize();
	login.style.width = 200;
	login.style.left = (bodySize[0]-200)/2+"px";
	login.style.top = (bodySize[1]/2-200)+"px";
	login.style.display = "block";
}


//设置DIV层的样式
function change(){
          var login = M("login");
      login.style.position = "absolute";
      login.style.border = "1px solid #CCCCCC";
      login.style.background ="#F6F6F6";
      var i=0;
          var bodySize = getBodySize();
      //login.style.left = (bodySize[0]-i*i*4)/2+"px";
      //login.style.top = (bodySize[1]/2-100-i*i)+"px";
	  login.style.left = 200;
	  login.style.top = 80;
      login.style.width =      i*i*4 + "px";
      login.style.height = i*i*1.5 + "px";
     
      popChange(i);
}
//让DIV层大小循环增大
function popChange(i){
      var login = M("login");
          var bodySize = getBodySize();
      login.style.left = (bodySize[0]-i*i*4)/2+"px";
      login.style.top = (bodySize[1]/2-100-i*i)+"px";

	  if (login.style.width < 980) {
		login.style.width = i*i*4 + "px";
	  }
	  if (login.style.height < 80) {
			login.style.height = i*i*1.5+ "px";
	  }
     
  
      if(i<=10){
           i++;
           setTimeout("popChange("+i+")",10);//设置超时10毫秒
      }
}
//打开DIV层
function openlogin()
{
        //change();
        showLogin();
        popCoverDiv()
        void(0);//不进行任何操作,如：<a href="#">aaa</a>
}
//关闭DIV层
function close(){
         M('login').style.display = 'none';
         M("cover_div").style.display = 'none';
        void(0);
}