Create an border arrow in css. Great for activity feeds and such.

border_arrow.css

.arrow {
  position: absolute;
  top: 15px;
  left: -11px;
  z-index: 100;

  .back {
    position: absolute;
    top: 0;
    left: 0;
    width: 0;
    height: 0;
    border-top: 10px solid rgba(0, 0, 0, 0);
    border-bottom: 10px solid rgba(0, 0, 0, 0);
    border-right: 10px solid #DDD;
  }
  .front {
    position: absolute;
    top: 2px;
    left: 3px;
    width: 0;
    height: 0;
    border-top: 8px solid rgba(0, 0, 0, 0);
    border-bottom: 8px solid rgba(0, 0, 0, 0);
    border-right: 8px solid #FFF;
  }
}