function initPage() {
	assignEvent( 'click', '*.popup_trigger',
		applyToDescendants, '*.popup', toggleVisibility );
	assignEvent( 'mouseover', '*.popup_trigger',
		applyToDescendants, '*.popup', showElement );
	assignEvent( 'mouseout', '*.popup_trigger',
		applyToDescendants, '*.popup', hideElement );
	}
	
addEvent(window, 'unload', purgeAllEvents);
addEvent(window, 'load', initPage);