jquery how to remove scroll bar in background when select is expanded,background :none doesnt works

$(document).ready(function(){
  $("#keyword_select").mouseover(function(){
    $("#keyword_select").css("height","200px","background-image","none"开发者_如何学Go).show(1000);

 });
 });

$(document).ready(function(){
  $("#keyword_select").mouseout(function(){
     $("#keyword_select").css("height","20px").show(1000);
 });
 });

the css

#keyword_select {
height:23px;
width:200px;
background-image:url(ddl.jpg);
background-position:right;
background-repeat:no-repeat;

}

and the html

<select id=#keyword_select multiple="multiple">
<option> first image </option>
<option> second image</option>
</select>

The parent container should have

overflow:hidden;

Here is a bit more information on the topic W3School Overflow