var selected_id = false;

function set_div (id) {

	var display = document.getElementById(id).style.display;
	
	if (display == 'block') {
		
		document.getElementById(id).style.display = 'none';
		
	} else {
		
		if (selected_id != false) {
		
			document.getElementById(selected_id).style.display = 'none';	
		}
		
		document.getElementById(id).style.display = 'block';
		selected_id = id;
	}
}