Proto.Tabs.js

<div class="tab-panel">
	<nav class="tabs">
		<ul>
			<li href="#sect-1" tabindex="1">tab 1</li>
			<li href="#sect-2" tabindex="2">tab 2</li>
			<li href="#sect-3" tabindex="3">tab 3</li>
		</ul>
	</nav>
	<section id="sect-1"></section>
	<section id="sect-2"></section>
	<section id="sect-3"></section>
</div>

<script>
document.delegate("nav.tabs li", "focus:in", function(event){
	Event.stop(event);
	this.addClassName("selected").siblings().invoke("removeClassName", "selected");
	var target = $(this.href.substring(tab.href.indexOf("#") + 1));
	if (target) target.show().siblings().slice(0).invoke("hide");
});
</script>