function mainResize() {
  var divBorderOffset = 4;

  var mainAdiv = document.getElementById('main_a');
  mainAdiv.style.height = '';

  var viewportHeight = window.innerHeight;
  var mainAdivHeight = mainAdiv.offsetHeight;
  var headerAdivHeight = document.getElementById('header_a').offsetHeight;
  var footerAdivHeight = document.getElementById('footer_a').offsetHeight;

  if ((headerAdivHeight + mainAdivHeight + footerAdivHeight) < viewportHeight) {
    mainAdiv.style.height = viewportHeight - headerAdivHeight - footerAdivHeight - divBorderOffset;
  }  
}

function n_over(item) {
  document.getElementById('n_' + item + '_i').src = '/media/n/n_' + item + '_a.gif';
  document.getElementById('n_' + item + '_a').style.color = "#FFFFFF";
  document.getElementById('n_' + item + '_a').style.textDecoration = "underline";
}

function n_out(item) {
  document.getElementById('n_' + item + '_i').src = '/media/n/n_' + item + '.gif';
  document.getElementById('n_' + item + '_a').style.color = '#DDDDDD';
  document.getElementById('n_' + item + '_a').style.textDecoration = 'none';
}