The following Facebook icon is made using pure CSS and only one HTML tag.

Facebook

How was it made?

The HTML:

<p class="logo">Facebook</p>

The CSS:

.logo {
	background: #4661b0;
	text-indent: -999em;
	width: 100px;
	height: 110px;
	border-radius: 3px;
	position: relative;
	overflow: hidden;
	border: 15px solid #4661b0;
	border-bottom: 0;
}
.logo:before {
	content: "/20";
	position: absolute;
	background: #4661b0;
	width: 40px;
	height: 90px;
	bottom: -30px;
	right: -37px;
	border: 20px solid white;
	border-radius: 25px;
}

.logo:after {
	content: "/20";
	position: absolute;
	width: 55px;
	top: 50px;
	height: 20px;
	background: white;
	right: 5px;
}