// JavaScript Document

    function toggle_visibility(id) {
       var f = document.getElementById(id);
       if(f.style.display == 'block')
          f.style.display = 'none';
       else
          f.style.display = 'block';
    }
	
    function open_image(b,c) {
       var f = document.getElementById(b);
	   var g = document.getElementById(c);
	   
		if(f.style.display == 'block')
	   		g.src = 'images/minus.gif';
		else
			g.src = 'images/plus.gif';

	}