function checkbox(id) {
	current=document.getElementById('hidden_'+id).value;
	if(current=="checked") {
		document.getElementById('hidden_'+id).value="";
		document.getElementById(id).src = "/images/checkbox_off.png";
	} else {
		document.getElementById('hidden_'+id).value="checked";
		document.getElementById(id).src = "/images/checkbox_on.png";
	}
}