CSS for popup with arrow.

gistfile1.css

.popup {
  position: relative;
  font-size: 12px;

  width: 300px;

  background-color: #28C0F7;
  color: white;

  padding: 15px;
  margin-left: 15px;

  -moz-border-radius: 10px;
  -webkit-border-radius: 10px;
  -o-border-radius: 10px;
  -ms-border-radius: 10px;
  -khtml-border-radius: 10px;
  border-radius: 10px;

  -moz-box-shadow: rgba(0, 0, 0, 0.8) 0 0 5px 0;
  -webkit-box-shadow: rgba(0, 0, 0, 0.8) 0 0 5px 0;
  -o-box-shadow: rgba(0, 0, 0, 0.8) 0 0 5px 0;
  box-shadow: rgba(0, 0, 0, 0.8) 0 0 5px 0;
}

h5 {
  margin: 0;
  font-size: 120%;
}

.popup .arrow {
  position: absolute;

  -moz-transform: rotate(45deg);
  -webkit-transform: rotate(45deg);
  -o-transform: rotate(45deg);
  transform: rotate(45deg);

  width: 30px;
  height: 30px;

  background-color: #28C0F7;
}

.left-arrow .arrow {
  left: -12px;
  top: 20px;
}
.right-arrow .arrow {
  right: -12px;
  top: 20px;
}