window.onload = function() {
  adjustNavigation();
}

function adjustNavigation() {
    var navigation, sidebar, maincontent;
    navigation  = xGetElementById('navigation');
    sidebar     = xGetElementById('sidebar');
    maincontent = xGetElementById('maincontent');
    h = xHeight(navigation);
    if (xHeight(sidebar) > h) { h = xHeight(sidebar); }
    if (xHeight(maincontent) > h) { h = xHeight(maincontent); }
    xHeight(navigation, h);
}