$(document).ready(function(){  
	var tallest = 0;
	$(".article").each(function() {
		tallest = tallest < $(this).height()? $(this).height() : tallest;
	});
	$(".nav_article").click(function() {
		var showIt = false;
		if ($(this).hasClass('next')) {
			if ($('.last_article:hidden').length) {
				showIt = $('.article:visible').next();
			}
		} else {
			if ($('.first_article:hidden').length) {
				showIt = $('.article:visible').prev();
			}
		}
		if (showIt) {
			$(".article").hide();
			showIt.fadeIn('fast');
		}
		return false;
	});
});