HTML

<a href="#" title="Facebook" class="btn btn-facebook btn-lg"><i class="fa fa-facebook fa-fw"></i> Facebook</a>

CSS

.btn-facebook {
	  background: #3B5998;
	  border-radius: 0;
	  color: #fff;
	  border-width: 1px;
	  border-style: solid;
	  border-color: #263961; 
	}
	.btn-facebook:link, .btn-facebook:visited {
	  color: #fff;
	}
	.btn-facebook:active, .btn-facebook:hover {
	  background: #263961;
	  color: #fff;
	}