clearInputValue = function(input, initial) {
	
	input 		= $(input);
	
	input.value = initial;
	
	input.onfocus = function() {
		if (input.value == initial) input.value = '';
	}

	input.onblur = function() {
		if (input.value == '') input.value = initial;
	}

}

Event.observe(window, 'load', function() {

	$('header_nav').immediateDescendants().each(function(child) {
		Event.observe(child, 'mouseover', function(event){
			$$('#header_nav .hover').invoke('removeClassName', 'hover');
			child.addClassName('hover');
		});
		Event.observe(child, 'mouseout', function(event){
			$$('#header_nav .hover').invoke('removeClassName', 'hover');
		});
	});

});