var last_id = false;

function show_div(div_id) {

	if (document.getElementById('nav' + div_id).style.display == 'none'){

		if (last_id != false){

			if ($('tab' + last_id)){
				document.getElementById('tab' + last_id).className = '';
			}

			if ($('nav' + last_id)){
				Effect.Fade('nav' + last_id);
			}

		}

		last_id = div_id;
		Effect.Appear('nav' + div_id);
		document.getElementById('tab' + div_id).className = 'hover';
	}
	else {
		last_id = false;
		Effect.Fade('nav' + div_id);
		document.getElementById('tab' + div_id).className = '';
	}

}