A CodePen by Niels Oeltjen. Rounded tabs - Simple css menu with rounded corners on the tabs and in the spaces between!

index.html

<nav>
  <ul>
	<li><a href="#">These</a></li><li><a href="#">Tabs</a></li><li><a href="#">Are</a></li><li><a href="#">Okay</a></li>
	</ul>
</nav>

style.css

@import url(http://fonts.googleapis.com/css?family=Dosis);

body {
  background: #ff2577;
  font-family: 'Dosis', sans-serif;
}
a {
  text-decoration: none;
  -webkit-transition: color 0.4s linear;
  -moz-transition: color 0.4s linear;
  -o-transition: color 0.4s linear;
	color: #ff2577;
}
a:hover {
	color: #272727;
}
nav {
	text-align: center;
	border-top: 14px solid white;
}
nav ul li {
	display: inline-block;
	position: relative;
  border-top: 10px solid white;
}
nav ul li a {
  font-size: 28px;
	line-height: 48px;
	display: block;
	background: white;
	padding: 0 20px;
	margin: -10px 10px 0 10px;
	text-transform: uppercase;
	letter-spacing: 1px;
	border-radius: 6px;
}
nav	ul li a:before,
nav	ul li a:after {
	background: #ff2577;
	text-indent: -999999px;
	overflow: hidden;
	border-radius: 6px;
	content: " ";
	width: 20px;
	display: block;
	position: absolute;
	z-index: 1;
}
nav	ul li a:before {
	left: -10px;
	top: -10px;
}
nav	ul li a:after {
	right: -10px;
	top: -10px;
}