使用JAVASCRIPT實現彈出框，過一段時間自動消失

<script> 
  var oPopup;
  var popTop=50;
  var mytime;
  function closemsg(){
   try{
    clearTimeout(mytime);
   }catch(e){}
   oPopup.hide();
  }
  
  function popshow(){
   //window.status=popTop;
   if(popTop>1160){
    closemsg();
    return;
   }
   if(popTop>1040&&popTop<1160){
    oPopup.show(screen.width-195,screen.height,250,1160-popTop);
   }
   if(popTop>1000&&popTop<1040){
    oPopup.show(screen.width-195,screen.height+(popTop-1160),250,116);
   }
   if(popTop<120){
    oPopup.show(screen.width-195,screen.height,250,popTop);
   }
   if(popTop<160){
    oPopup.show(screen.width-195,screen.height-popTop,250,116);
   }
   popTop+=10;
   mytime=setTimeout("popshow();",100);
  }
  
  function popmsg(msgnum,msgstr){
   oPopup = window.createPopup();
   var winstr='<table style="border-top: #FFFFFF 1px solid; border-left: #FFFFFF 1px solid" cellSpacing=0 cellPadding=0 width="100%" bgcolor=#cfdef4 border=0>';
   winstr   +='  <tr>';
   winstr   +='   <td style="font-size: 12px; background-image: url(msgTopBg.gif); color: #0f2c8c" width=30 height=24></td>';
   winstr   +='   <td style="font-weight: normal; font-size: 12px; background-image: url(msgTopBg.gif); color: #1f336b; padding-top: 4px;padding-left: 4px" valign=center width="100%"> 管理平臺消息提示：</td>';
   winstr   +='   <td style="background-image: url(msgTopBg.gif); padding-top: 2px;padding-right:2px" valign=center align=right width=19><span title=關閉 style="cursor: hand;color:red;font-size:12px;font-weight:bold;margin-right:4px;" οnclick="window.parent.closemsg();">×</span></td>';
   winstr   +='  </tr>';
   winstr   +='  <tr>';
   winstr   +='   <td style="padding-right: 1px; background-image: url(1msgBottomBg.jpg); padding-bottom: 1px" colSpan=3 height=90>';
   winstr   +='    <div style="border-right: #b9c9ef 1px solid; padding-right: 13px; border-top: #728eb8 1px solid; padding-left: 13px; font-size: 12px; padding-bottom: 13px; border-left: #728eb8 1px solid; width: 100%; color: #1f336b; padding-top: 6px; border-bottom: #b9c9ef 1px solid; height: 100%">'
   winstr   +='                    您有<font color=#FF0000>'+msgnum+'</font>條新短消息<br><br>';
   winstr   +='           <div align=center style="word-break:break-all">';
   winstr   +=msgstr;
   winstr   +='     </div>';
   winstr   +='    </div>';
   winstr   +='   </td>';
   winstr   +='  </tr>';
   winstr   +='</table>';
    
   oPopup.document.body.innerHTML = winstr;
   popshow();
  }
  <!--上面是定議，下面是調用-->
  popmsg(1,'msg');
</script>