styles.css

.arrow_box {
	position: relative;
	background: #ddd;
	border: 4px solid #fff;
}
.arrow_box:after, .arrow_box:before {
	left: 100%;
	top: 50%;
	border: solid transparent;
	content: "";
	height: 0;
	width: 0;
	position: absolute;
}

.arrow_box:after {
	border-color: rgba(221, 221, 221, 0);
	border-left-color: #ddd;
	border-width: 20px;
	margin-top: -20px;
}
.arrow_box:before {
	border-color: rgba(255, 255, 255, 0);
	border-left-color: #fff;
	border-width: 26px;
	margin-top: -26px;
}