function setOpacity( elem, level ) {
    elem.style.filter = "alpha(opacity="+level+")";
    elem.style.opacity = level / 100;
}

// powr >  = easi in ; powr < 1 = ease out ; powr = 1 linear
function moveLeft(elem,startPos,endPos,intervals) {
  var q=0;
    leftTimer = setInterval(
	function() {
	  if (q <= endPos){
	  setLeftPos(elem,startPos-q);
      q+=20;
      }
      else {
        clearInterval(leftTimer);
      }
	}
	,intervals)
}

// powr >  = easi in ; powr < 1 = ease out ; powr = 1 linear
function moveRight(elem,startPos,endPos,intervals) {
  var q=0;
    rightTimer = setInterval(
	function() {
	  if (q <= endPos){
	  setLeftPos(elem,startPos+q);
      q+=20;
      }
      else {
        clearInterval(rightTimer);
      }
	}
	,intervals)
}

function setLeftPos(elem,pos) {
  elem.style.left = pos +"px";
}