var item = {N1: "ask", N2: "recent", N3: "experts", N4: "interview"};

function change_tab(id, hash) {
	var request = new Sys.Net.WebRequest();
	var executor = new Sys.Net.XMLHttpExecutor();
	request.set_url('tab/' + item[id] + '.aspx?' + Math.random());
	request.add_completed(MyCompleted);
	request.set_executor(executor); 
	request.invoke();
	function MyCompleted(executor, eventArgs){
		if(executor.get_responseAvailable()) {
			$get('ContentsArea').innerHTML = executor.get_responseData();
		}
		if(hash){
			location.hash = hash;
		}
	}
	chCSS(id);
}

function chCSS(id){
   for(i=1; i<5; i++) {
      $get('Tab_' + item['N' + i]).src = 'images/tab_' + item['N' + i] + '.gif';
   }
   $get('Tab_' + item[id]).src = 'images/tab_' + item[id] + '_here.gif';
   $get('TabBottomImage').src = 'images/tab_bottom_' + item[id] + '.gif';
   $get('TabBottom').style.backgroundImage = 'url(images/tab_bg_' + item[id] + '.gif)';
}