javaScript遮罩

<style type="text/css">
        #container {}
        #pagetitle {font-size: 20px; font-weight: bold; width: 100%; text-align: center; }
   </style>

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     jQuery(function() {
      var today = new Date();
      var yesterday = today.setDate(today.getDate()-1);
      jQuery("#day").datepicker({ dateFormat: "yy-mm-dd",maxDate: new Date(yesterday) });
   
   var container=document.getElementById("container");
      container.style.height=(document.body.clientHeight-20)+"px";
     });

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function sendEmail(){

var url = "$rc.contextPath/sendEmailDayReport.do";
             var param = {"day":$("#day").val()};
    
    $("#show").css("display","");
       $("#bg").css("display","");
   
      $("#data").load(url, param,function(res,status,xhr) {
        $("#show").css("display","none");
           $("#bg").css("display","none");
       //("success", "notmodified", "error", "timeout" 或 "parsererror")
           if(status == 'success'){
            res = eval("(" + res + ")");
         if(res=="1"){
            alert("郵件發送成功！");
         }else if(res=="0"){
            alert("郵件發送失敗！");
         }else{
            alert("系統發生異常！");
         }
     }else if(status =='error'){
         alert("ajax操做失敗!");
     }
        });

}

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 <div id="container" style="overflow-y:auto;padding-top:20px;">
    <div id="bg" style="display:none;width:100%; height:100%; background:#aaa; filter:alpha(Opacity=50); position:absolute; left:0; top:0;"></div>
    <div id="show" style="display:none;padding:8px 0 8px 44px; margin-left:-80px; position:absolute; left:50%; top:344px; z-index:2; color:#000; background:url(images/loading.gif) no-repeat;">郵件發送中,請稍後...</div>
    <div id="data" style="display:none"></div>