To set the triangle at the center and at the bottom of div, use the following. You need to set left to 50% −
.demo: after { position: absolute; border-top: solid 50px #e15915; border-left: solid 50px transparent; border-right: solid 50px transparent; top: 100%; left: 50%; margin-left: -50px; width: 0; height: 0; }