gistfile1.js

var box = $('yourBoxName');
var tabs = box.select('h3');
var bodies = box.select('p,ul,table,dl');
var tabStyle = 'background-color:#ccc';
var tabSelected = 'background-color:#dd9';
tabs.invoke('setStyle','display:inline; font-size:0.9em; padding:0.3em 1em; ' + tabStyle + '; margin:0 1px 0 0; cursor:pointer');
bodies.each(function(elm){
  elm.hide();
  elm.setStyle('float:left; width:100%');
  elm._tab = elm.previous('h3'); 
  box.insert({bottom:elm.remove()}); 
});
tabs.first().setStyle(tabSelected);
var bar = new Element('ul',{style:'list-style-type:none;padding:0;margin:-1.9em 0 0 -8px'});
box.insert({top:bar});
tabs.each(function(elm){
  bar.insert(elm.wrap('li'));
});
bar.select('li').invoke('setStyle','list-style-type:none; display:inline;');
tabs.invoke('observe','click',function(evt){
  bodies.invoke('hide');
  tabs.invoke('setStyle',tabStyle);
  var tab = this;
  tab.setStyle(tabSelected);
  var bods = bodies.findAll(function(elm){
    return elm._tab == tab;
  }); 
  bods.invoke('show');
});
bodies.findAll(function(elm){
  return elm._tab == tabs.first();
}).invoke('show');