function focusTab(tab, tabbg) {
	document.getElementById('features').className = 'hidden';
	document.getElementById('manuals').className = 'hidden';
	document.getElementById(tab).className = 'visible';

	document.getElementById('tabfeatures').className = 'hidetab';
	document.getElementById('tabmanuals').className = 'hidetab';
	document.getElementById(tabbg).className = 'showtab';
}