var guideFields;

function initGuide()
{
    guideFields = document.getElementsByClassName('guide');
    // add focus handler
    guideFields.each(function(elem)
    {
       // elem.cleared = false;
        Event.observe(elem, 'focus', clearGuide.bindAsEventListener(elem));
    })
}

function clearGuide(ev)
{
   var elem = eventTarget(ev);
   try
   {
	    elem.value = '';
	    Event.stopObserving(elem, 'focus', clearGuide);
	}
	catch(e)
	{
	   //for(i in ev) alert(i);
	}
}

function eventTarget(ev)
{
	// get event element from different event object models
	if(typeof ev.target != 'undefined') return ev.target;
	if(typeof ev.srcElement != 'undefined') return ev.srcElement;
	return {};
}
Event.observe(window, 'load', initGuide);