/* class */
		var TabSet = new Class({
			options: {
				activeClass: 'active', //css class
				cookieName: '',
				cookieOptions: {
					duration: 30, //30 days
					path: '/'
				},
				startIndex: 0 //start with this item if no cookie or active
			},
			Implements: [Options,Events],
			initialize: function(tabs,contents,options) {
				//handle arguments
				this.setOptions(options);
				this.tabs = $$(tabs);
				this.contents = $$(contents);
				//determine the "active" tab
				var active = (Cookie.read(this.options.cookieName) || this.options.startIndex);
				this.activeTab = this.tabs[active].addClass(this.options.activeClass);
				this.activeContent = this.contents[active].setStyle('height','auto');
				//process each tab and content
				this.tabs.each(function(tab,i) {
					this.processItem(tab,this.contents[i],i);
				},this);
				//tabs are ready -- load it!
				this.fireEvent('load');
			},
			processItem:function(tab,content,i) {
				var contentHeight = content.getScrollSize().y;
				//add a click event to the tab
				tab.addEvent('click',function(e) {
					//stop!
					if(e) e.stop();
					//if it's not the active tab
					if(tab != this.activeTab) {
						//remove the active class from the active tab
						this.activeTab.removeClass(this.options.activeClass);
						//make the clicked tab the active tab
						(this.activeTab = tab).addClass(this.options.activeClass);
						//tween the old tab content up
						//tween the new content down
						this.activeContent.set('tween',{
							onComplete:function() {
								this.activeContent = content.fade('in').set('tween',{ onComplete: $empty }).tween('height',contentHeight);
								//fire the tab change event
								this.fireEvent('change',[tab,content]);
							}.bind(this)
						}).setStyles({
							height: contentHeight,
							overflow: 'hidden'
						}).fade('out').tween('height',0);
						//save the index to cookie
						if(this.options.cookieName) Cookie.write(this.options.cookieName,i,this.options.cookieOptions);
					}
				}.bind(this));
			}
		});
		
		
		/* usage */
		window.addEvent('load',function() {
			var tabset = new TabSet($$('#tabs1 li a'),$$('#contents1 li'),{
				cookieName: 'demo-list'
			});
		});