Mine

<html><head><script src="prototype.js" type="text/javascript" charset="iso-8859-1"></script><script type="text/javascript" charset="iso-8859-1">Event.observe( window, 'load', function(){	Event.observe( $('teste'), 'click', function(){		var pars = '&id=1'; // caso use um parametro		new Ajax.Request('helloWord.php', { method: 'post', parameters: pars, onComplete: function(ret){ 			alert(ret.responseText);		}});	});});</script></head><body><button id="teste">Click me</button></body></html>