Event.observe(window, 'load', init, false);

function init() {
   Event.observe($('requestPass'), 'click', requestPassword, false);
}

function requestPassword() {
   var email = prompt('Please enter your email address');
   var params = 'email='+escape(email);
   var myAjax = new Ajax.Request(
      'requestPassword.php',{
         method: 'post',
         parameters: params,
         asynchronous: false
      });
   alert(myAjax.transport.responseText);
}