var sgs_current = 1;
function goto_page(p, id) {
  if (typeof(id) == 'undefined') {
    id = 'living-green-boxnav';
  }
  
  p = +p; // Typecast as integer
  if (p == sgs_current) { return; }
  
  var el = document.getElementById('page' + p);
  var c  = document.getElementById('page' + sgs_current);
  if (!el) { return; }
  
  var link_new = document.getElementById(id + p);
  var link_old = document.getElementById(id + sgs_current);
  if (link_new) { link_new.className = 'living-green-boxnavOn'; }
  if (link_old) { link_old.className = 'living-green-boxnav'; }
  
  c.style.display  = 'none';
  el.style.display = 'block';
  sgs_current = p;
}