让showModalDialog适应firefox

<input   type="button"   value="打开对话框"   onclick="showDialog('#')"/>  
  <SCRIPT   LANGUAGE="JavaScript">  
  <!--  
  function   showDialog(url)  
  {  
  if(   document.all   ) //IE  
  {  
  feature="dialogWidth:300px;dialogHeight:200px;status:no;help:no";  
  window.showModalDialog(url,null,feature);  
  }  
  else  
  {  
                                        //modelessDialog可以将modal换成dialog=yes  
  feature   ="width=300,height=200,menubar=no,toolbar=no,location=no,";  
  feature+="scrollbars=no,status=no,modal=yes";    
  window.open(url,null,feature);  
  }  
  }  
  //-->  
  </SCRIPT>