function turn_over(psImageName) {
  document.getElementById(psImageName).src = '/images/navigation/'+psImageName+'_over.gif';
}
function turn_off(psImageName) {
  if (psImageName != gsPage) {
    document.getElementById(psImageName).src = '/images/navigation/'+psImageName+'.gif';
  }
}
function SetMainButton() {
  document.getElementById(gsPage).src = '/images/navigation/'+gsPage+'_over.gif';
}