This is a control render by browsers rendering engine & some CSS property may not work on it. In order to meet your goal try to make some customize controll like this
html markup:
<ul id="test">
<li>1239187239172391823kajsasdfaasdfas9817293971293</li>
<li>1239187239172391823kajsasdfaasdfas9817293971293</li>
<li>1239187239172391823kajsasdfaasdfas9817293971293</li>
<li>1239187239172391823kajsasdfaasdfas9817293971293</li>
</ul>
CSS:
#test li{
display:block;
background-color:#CCCCCC;
border:1px #FFF solid;
display:none;
width:auto;
cursor:pointer;
}
#test li:hover{
background-color:#999999;
}
jQuery:
$("#test li:first").css({'width':150+'px','display':'block', 'border':'1px #000 solid', 'overflow':'hidden', 'cursor':'pointer'});
$("#test li:first").toggle(function(){
$(this).siblings().css({'display':'list-item','width':'auto'});
},
function(){
$(this).siblings().css({'display':'none'});
}
This just a rough sketch of it.