<script type="text/javascript">
function toggle() {
  theObj = document.getElementById('Sunyanzi').style;
  if (  theObj.display == "none" ) theObj.display = "block"; else theObj.display = "none";
}
</script>
<div id="Sunyanzi" style="display:none">你看我出现了~~~</div>
<br />
<input type="button" onclick="toggle()" value="点一下试试看 ...?" />

两种方法：去除和隐藏

//创建你的弹出层  
    var dvMsg = document.createElement("div"); 
    strHtml =  "<div class='####'>弹出层内容</div>"
    strHtml += " <div class='####'><input type='button' value='关闭' onclick='btnclick()'></div>"
    dvMsg.innerHTML = strHtml;   
    document.body.appendChild(dvMsg);
// 关闭按钮    
btnclick = function (){                      
    document.body.removeChild(dvMsg);

-------------------------
或者 弹出层用div id标记

<div id="tanchu">弹出层内容</div>

js里
function open(){
document.getElementById(tanchu).style.display="";  //显示
}
function close(){
document.getElementById(tanchu).style.display="none";  //不显示（页面初始化的时候同样加载一遍）
}