var idInterval;

function Animuj()
{
  var table_1 = document.getElementById('table_1');
  var table_2 = document.getElementById('table_2');

  if (parseInt(table_1.style.left) < -546)
  {
    table_1.style.left = "546px";
  }
  else
  {
    table_1.style.left = (parseInt(table_1.style.left) - 1)+"px";
  }

  if (parseInt(table_2.style.left) < -546)
  {
    table_2.style.left = "546px";
  }
  else
  {
    table_2.style.left = (parseInt(table_2.style.left) - 1)+"px";
  }
}

function start()
{  
  idInterval = window.setInterval("Animuj()", 20);
}

function stop()
{
  window.clearInterval(idInterval);
}