window.open打开页面居中显示

<script type="text/javascript">

function openwindow(url,name,iWidth,iHeight)
 {
  var url;                            //转向网页的地址;
  var name;                           //网页名称，可为空;
  var iWidth;                         //弹出窗口的宽度;
  var iHeight;                        //弹出窗口的高度;
  //window.screen.height获得屏幕的高，window.screen.width获得屏幕的宽
  var iTop = (window.screen.height-30-iHeight)/2;       //获得窗口的垂直位置;
  var iLeft = (window.screen.width-10-iWidth)/2;        //获得窗口的水平位置;
  window.open(url,name,'height='+iHeight+',,innerHeight='+iHeight+',width='+iWidth+',innerWidth='+iWidth+',top='+iTop+',left='+iLeft+',toolbar=no,menubar=no,scrollbars=auto,resizeable=no,location=no,status=no');
 }

</script>

 <div class="itemspace">  
     Tag标签:  
     <input name="Editor$Edit$Advanced$txbTag" type="text" id="Editor_Edit_Advanced_txbTag" style="width: 500px" />   
     <a onclick="leftVal = (screen.width - 300) / 2;topVal = (screen.height - 500) / 2;window.open( 'InsertTag.aspx','_blank','width=300,height=500,toolbars=yes,resizable=yes,scrollbars=yes,left='+leftVal+',top='+topVal);return false" href="#">插入已有标签</a> (多个关键字之间用“,”分隔，最多不超过10个)</div>  
    <div class="itemspace">