function showObr(obr)
{
  switch (obr)
  {
      case 'obr1':
          document.getElementById('obr1').style.display = 'inline';
          document.getElementById('obr2').style.display = 'none';
          document.getElementById('obr3').style.display = 'none';
          document.getElementById('obr4').style.display = 'none';

          document.getElementById('obr1_link').className = 'active';
          document.getElementById('obr2_link').className = 'norm';
          document.getElementById('obr3_link').className = 'norm';
          document.getElementById('obr4_link').className = 'norm';
      break;

      case 'obr2':
          document.getElementById('obr1').style.display = 'none';
          document.getElementById('obr2').style.display = 'inline';
          document.getElementById('obr3').style.display = 'none';
          document.getElementById('obr4').style.display = 'none';

          document.getElementById('obr1_link').className = 'norm';
          document.getElementById('obr2_link').className = 'active';
          document.getElementById('obr3_link').className = 'norm';
          document.getElementById('obr4_link').className = 'norm';
      break;

      case 'obr3':
          document.getElementById('obr1').style.display = 'none';
          document.getElementById('obr2').style.display = 'none';
          document.getElementById('obr3').style.display = 'inline';
          document.getElementById('obr4').style.display = 'none';

          document.getElementById('obr1_link').className = 'norm';
          document.getElementById('obr2_link').className = 'norm';
          document.getElementById('obr3_link').className = 'active';
          document.getElementById('obr4_link').className = 'norm';
      break; 

      case 'obr4':
          document.getElementById('obr1').style.display = 'none';
          document.getElementById('obr2').style.display = 'none';
          document.getElementById('obr3').style.display = 'none';
          document.getElementById('obr4').style.display = 'inline';

          document.getElementById('obr1_link').className = 'norm';
          document.getElementById('obr2_link').className = 'norm';
          document.getElementById('obr3_link').className = 'norm';
          document.getElementById('obr4_link').className = 'active';
      break;
  }
}

var article = 1;
var timer;

function startSlideShow()
{
  showObr('obr' + article);

  article = article + 1;

  if (article > 4) article = 1;

  timer = setTimeout("startSlideShow()", 2000);
}