function showNavigation (elName) {
  var breakOut = false
  if($(elName + '_nav').style.display == 'block')
  {
    hideNavigation(elName + '_nav')
    breakOut = true
  }  
  
  hideElements('.overlay_nav')
  hideElements('.overlay_header_main_nav')  
  hideElements('.overlay_header_top_nav')  
  
  if(breakOut)
  {
    return 0
  }
  
  $(elName + '_header').setStyle({
    display: 'block'
  })
  $(elName + '_nav').setStyle({
    display: 'block'
  })
}

function hideElements (className) {
  $$(className).each(function(el){
    hideNavigation(el)
  })
}

function hideNavigation (el) {
  $(el).setStyle({
    display: 'none'
  })
}