function form_action(action) {
	var frm = document.forms[0];
	frm._action.value = action;
	frm.action = "/image_viewer.php?image_id=" + frm.image_id.value;
	if(frm.exhibition_id.value > 0) frm.action += "&exhibition_id=" + frm.exhibition_id.value;
	frm.submit();
}