Cacher is the code snippet organizer for pro developers

	if (sessionStorage.getItem('advertOnce') == null) {
		$('.modal_con').css('display', 'block');
		sessionStorage.setItem('advertOnce', 'true');
	}
	
// 	more details on https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_storage_getitem_session