CSS: Shapes

css3shapes.css

/**
 *  CSS3 Usual Shapes
 */

/* Arrow 1  */
#left-triangle {
   width: 0;
   height: 0;
   border-right: 5px solid gray;
   border-top: 5px solid transparent;
   border-bottom: 5px solid transparent;
}
#left-triangle:after {
    content: '';
    display: block;
    width: 0;
    height: 0;
    border-right: 5px solid white;
    border-top: 5px solid transparent;
    border-bottom: 5px solid transparent;
    margin: -5px 0 0 2px;
}