CSS triangle :before element

You need to specify the content property.

For positioning, add position:relative to the parent, and then absolutely position the arrow -15px to the left.

jsFiddle example

.d {
    position:relative;
}

.d:before {
    content:"\A";
    border-style: solid;
    border-width: 10px 15px 10px 0;
    border-color: transparent #dd4397 transparent transparent;
    position: absolute;
    left: -15px;
}