var TimeToFade = 1000.0;
var elementnum = 0;
var fading = 0;
var elementarray = new Array ();
elementarray[0]="bio1";
elementarray[1]="bio2";
elementarray[2]="bio2";
elementarray[3]="bio1";

function prefade() {

  eid = elementarray[elementnum];

    if (document.getElementById(eid).style.display == "none") {
      document.getElementById(eid).style.display = "block";
    }

  fade (eid);
  
}



function fade(eid)
{
  fading = 1;
  var element = document.getElementById(eid);
  if(element == null)
    return;
    
   
  if(element.FadeState == null)
  {
    if((element.style.opacity == null || element.style.opacity == '' 
       || element.style.opacity == '1'))
      element.FadeState = 2;
    else
      element.FadeState = -2;
  }
    
  if(element.FadeState == 1 || element.FadeState == -1)
  {
    element.FadeState = element.FadeState == 1 ? -1 : 1;
    element.FadeTimeLeft = TimeToFade - element.FadeTimeLeft;
  }
  else
  {
    element.FadeState = element.FadeState == 2 ? -1 : 1;
    element.FadeTimeLeft = TimeToFade;
    setTimeout("animateFade(" + new Date().getTime() + ",'" + eid + "')", 33);
  }  
}

function animateFade(lastTick, eid)
{  
  var curTick = new Date().getTime();
  var elapsedTicks = curTick - lastTick;
  
  var element = document.getElementById(eid);

  if(element.FadeTimeLeft <= elapsedTicks)
  {
    element.style.opacity = element.FadeState == 1 ? '1' : '0';
    element.style.filter = 'alpha(opacity = ' + (element.FadeState == 1 ? '100' : '0') + ')';
    element.FadeState = element.FadeState == 1 ? 2 : -2;
    if (element.style.opacity == 0) {
      element.style.display="none";
    }

    elementnum++;
    if (elementnum==2) {
      fading = 0;
      return;
    }
    if (elementnum==4) {
      elementnum = 0;
      fading = 0;
      return;
    }

    eid = elementarray[elementnum];

    if (document.getElementById(eid).style.display == "none") {
      document.getElementById(eid).style.display = "block";
    }
    
    fade (eid);
    return;
  }
 
  element.FadeTimeLeft -= elapsedTicks;
  var newOpVal = element.FadeTimeLeft/TimeToFade;
  if(element.FadeState == 1)
    newOpVal = 1 - newOpVal;

  element.style.opacity = newOpVal;
  element.style.filter = 'alpha(opacity = ' + (newOpVal*100) + ')';
  
  setTimeout("animateFade(" + curTick + ",'" + eid + "')", 33);
}