function showParts(parts) {
	for (var i=0; i < parts.length; i++) {
		var elem = document.getElementById(parts[i]);
		if (elem) {
			elem.style.visibility = 'visible';
		}
	}
}

function showMainParts() {
	var parts = ['header', 'main_news', 'footer'];
	showParts(parts);
}