Triangle Bug

HTML

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

CSS

#container
{
    width:200px; height:200px;
     background:yellow;
}
#triangle
{
    position:absolute;
    top:20px; left:20px;
    width:0; height:0;
    border-width:50px; border-color:pink transparent transparent pink;
    /* border-style: solid; /* No */
    /* border-style: outset; /* No */
    border-style: solid outset solid solid;
}