function RandomNumber() 
{
  var today = new Date();
  var num= Math.abs(Math.sin(today.getTime()/1000));
  return num;
}

function RandomGraphics() 
{
  var x = RandomNumber();

if (x > .00) 
{document.write("<img src='images/pixel_red.gif' width='120' height='1400' />"); return; 
}

}

RandomGraphics();