function show_tab(tab) {
	if (tab == 'left') {
		document.getElementById('tab-content-left').style.display = "";
		document.getElementById('tab-left').className = "tab-act";
		document.getElementById('tab-content-right').style.display = "none";
		document.getElementById('tab-right').className = "tab-no";
	} else {
		document.getElementById('tab-content-left').style.display = "none";
		document.getElementById('tab-left').className = "tab-no";
		document.getElementById('tab-content-right').style.display = "";
		document.getElementById('tab-right').className = "tab-act";
	}
	new Ajax.Request('/submission/tab_session.php',
		{
			method: 'get',
			parameters: {tabpos: tab}
		}
	);
}