function showMenu(menuNumber) {
  var currentMenu = document.getElementById("menu-container-" + menuNumber);
  var currentWindowWidth = getWindowWidth();
  var currentLeft;
  var newLeft;
  var minimumWindowWidth = 760;
  var leftOffset = 163;

  if (currentMenuNumber != menuNumber) {
    hideMenusNow();
  }
  
  newLeft = ((currentWindowWidth < minimumWindowWidth) ? leftOffset : (getWindowWidth() / 2) - (minimumWindowWidth / 2) + leftOffset);
  // setting the left position in netscape is a little different than IE
  currentMenu.style ? currentMenu.style.left = newLeft + "px" : currentMenu.left = newLeft;

  currentMenu.style.visibility = "visible";
  currentMenuNumber = menuNumber;
}

function hideMenusNow() {
  if (currentMenuNumber == 0) {
    for (i=1; i<=numberOfMenus; i++) {
        document.getElementById("menu-container-" + i).style.visibility = "hidden";
    }
  }
}

function hideMenus() {
  currentMenuNumber = 0;
  setTimeout("hideMenusNow()",700);
}

// this function calculates the window's width - different for IE and netscape
 function getWindowWidth()
 {
   return window.innerWidth ? window.innerWidth : document.body.offsetWidth;
 }