三角形のcss実装(IE 6互換)

.triangle_up{
    width: 0;
    height:0;
    overflow: hidden;
    border-left: 4px solid transparent;
    border-right: 4px solid transparent;
    border-bottom: 4px solid #ca0309;
    _border-left: 4px solid #fff;
    _border-right: 4px solid #fff;
}