层在浏览器的优先级比较低,下面是显示的优先级
div<select<iframe,
除非你把listbox也做在层上,否则我认为是没有办法解决的

解决方案 »

  1.   

    <select>
    <option>sf</option>
    <option>sdf</option>
    </select>
    <script>
    var toshow='<iframe style="width:100%"  height=36  src="about:<body topmargin=5 scroll=no><center>我经常访问的网站</center>"></iframe>';
    function ex(n){Expository1.innerHTML=n;Expository1.style.top=0
    Expository1.style.left=0
    Expository1.style.visibility="visible"}
    function ex1(){Expository1.style.visibility="hidden"}
    </script>
    <div id=Expository1 style="position:absolute;z-index:2;width:250;border-style:double;border-color:#FF66FF;background-color:#FFCCFF; visibility:hidden" align=left></div>
    <p><p>
    <a href="http://www.csdn.net" onmouseover=ex(toshow) onmouseout=ex1()>显示说明</a>
      

  2.   

    IE6还可以
    <select>
    <option>sf</option>
    <option>sdf</option>
    </select>
    <script>
    var pop=createPopup()
    pop.document.body.innerHTML="test";
    pop.show(window.screenLeft,window.screenTop+20,100,20);
    </script>
      

  3.   

    如果要正好覆盖select,可以用
    <select id=t>
    <option>sf</option>
    <option>sdf</option>
    </select>
    <script>
    var pop=createPopup()
    pop.document.body.innerHTML="test";
    pop.show(window.screenLeft+t.offsetLeft,window.screenTop+t.offsetTop,t.offsetWidth,t.offsetHeight);
    </script> 
      

  4.   

    <HTML><HEAD><TITLE>如何盖住(下拉列表框) Select ?</TITLE>
    <META http-equiv="Content-Type" content="text/html; charset=gb2312"></HEAD><BODY text="#000000" bgcolor="#ffffff" ms_positioning="GridLayout"><INPUT type="text" name="textfield"><br><SELECT name="select">
    <OPTION value="fdsa" selected>fdsa</OPTION>
    </SELECT><br><iframe></iframe><OBJECT style="Z-INDEX: 1000; LEFT: 47px; WIDTH: 152px; POSITION: absolute; TOP: 5px; HEIGHT: 200px" type="text/x-scriptlet"  data="about:这是盖住下拉框的东东"></OBJECT>
    </BODY>
    </HTML><HTML><HEAD><TITLE>如何盖住(下拉列表框) Select ?</TITLE>
    <META http-equiv="Content-Type" content="text/html; charset=gb2312"></HEAD><BODY text="#000000" bgcolor="#ffffff" ms_positioning="GridLayout"><INPUT type="text" name="textfield"><br><SELECT name="select">
    <OPTION value="fdsa" selected>fdsa</OPTION>
    </SELECT><br><iframe></iframe><OBJECT style="Z-INDEX: 1000; LEFT: 47px; WIDTH: 152px; POSITION: absolute; TOP: 5px; HEIGHT: 200px" type="text/x-scriptlet"  data="about:这是盖住下拉框的东东"></OBJECT>
    </BODY>
    </HTML><HTML><HEAD><TITLE>如何盖住(下拉列表框) Select ?</TITLE>
    <META http-equiv="Content-Type" content="text/html; charset=gb2312"></HEAD><BODY text="#000000" bgcolor="#ffffff" ms_positioning="GridLayout"><INPUT type="text" name="textfield"><br><SELECT name="select">
    <OPTION value="fdsa" selected>fdsa</OPTION>
    </SELECT><br><iframe></iframe><OBJECT style="Z-INDEX: 1000; LEFT: 47px; WIDTH: 152px; POSITION: absolute; TOP: 5px; HEIGHT: 200px" type="text/x-scriptlet"  data="about:这是盖住下拉框的东东"></OBJECT>
    </BODY>
    </HTML>