Triangle Bug

HTML

<div id="container">
    <div id="triangle">
    </div>
</div>

CSS

#container
{
    width:200px; height:200px;
     background:red;
}
#triangle
{
    position:absolute;
    top:20px; left:20px;
    width:0; height:0;
    border-width:50px; border-style:solid; border-color:#FFF transparent transparent #FFF;
}