gistfile1.js

//= require "http://gist.github.com/66568"
//= require "http://gist.github.com/162593"

<div class="tab_panel">
	<nav>
		<ul>
			<li class="tab selected" tabindex="1">tab 1</li>
			<li class="tab" tabindex="2">tab 2</li>
			<li class="tab" tabindex="3">tab 3</li>
		</ul>
	</nav>
	<section></section>
	<section style="display: none;"></section>
	<section style="display: none;"></section>
</div>
			
document.delegate('.tab_panel .tab', 'focus:in', function(){
	this.up('.tab_panel').select('section').invoke('hide')[this.previousSiblings('.tab').length].show();
	this.up().select('.selected').invoke('removeClassName', 'selected');
	this.addClassName('selected');
});