HTML按钮实现！！！文件上传，遮罩层

 <input type="file" />

<style type="text/css">
         #bg{ display: none;  position: absolute;  top: 0%;  left: 0%;  width: 100%;  height: 100%;  background-color: black;  z-index:1001; opacity: 0.7;  opacity:.70;  filter: alpha(opacity=70);}
         #show{display: none;  position: absolute;  top: 25%;  left: 22%;  width: 53%;  height: 49%;  padding: 8px;  border: 8px solid #E8E9F7;  background-color: white;  z-index:1002;  overflow: auto;}
        
     </style>

 <input id="btnshow" type="button" value="Show" onclick="showdiv();" />
     <div id="bg"></div>
     <div id="show">测试
         <input id="btnclose" type="button" value="Close" onclick="hidediv();" />

 <script language="javascript" type="text/javascript">
         function showdiv() {            
             document.getElementById("bg").style.display = "block";
             document.getElementById("show").style.display = "block";
         }
         function hidediv() {
             document.getElementById("bg").style.display = ‘none‘;
             document.getElementById("show").style.display = ‘none‘;
         }
     </script>