直接上代码：
<style>
*{
margin:0;
padding: 0;
}
#bg{
width: 100%;
height: 100%;
z-index: 999;
position: absolute;
left: 0%;
top: 0%;
background-color: rgba(0,0,0,0.8);
filter: alpha(opacity=80);
display: none;
}
#content{
z-index: 1000;
width: 50%;
height: 50%;
position: absolute;
left: 20%;
top: 20%;
background: white;
padding: 30px;
display: none;
}
</style>
<div id="bg">
</div>
<div id="content">
<input type="text" value="" id="txt">
<input type="submit" onclick="document.getElementById('bg').style.display='none';document.getElementById('content').style.display='none';var txt=document.getElementById('txt').value;document.getElementById('back').innerText=txt; ">
</div>
<div id="index"><a href="javascript:void(0);" onclick="document.getElementById('bg').style.display='block';document.getElementById('content').style.display='block'; ">点击弹出窗口</a></div>
<div id="back"></div>
