function sliderInit(background_id,thumb_id,label_id) {
  var slider = YAHOO.widget.Slider.getHorizSlider(background_id, thumb_id, 77, 77, 22);
  slider.animate = false;

  slider.subscribe("change", function() {
    var valueNow = slider.getValue();
    var valueMin = slider.thumb.rightConstraint;
    var valueMax = slider.thumb.leftConstraint;

    var result = 0 - (valueMax - valueMin - valueNow) / 22;
    result = Math.round(result);
    var casenum = result + 4;
    if (navigator.userAgent.indexOf("WebKit")>=0 && navigator.userAgent.indexOf("WebKit/5")==-1) {
        // if browser uses WebKit decrese the value by one due to a yahoo slider bug
        casenum--;
    }
    var message = '';
    switch (casenum) {
    case 1: message='3 grades easier'; break;
    case 2: message='2 grades easier'; break;
    case 3: message='1 grade easier'; break;
    case 4: message='same reading level'; break;
    case 5: message='1 grade harder'; break;
    case 6: message='2 grades harder'; break;
    case 7: message='3 grades harder'; break;
    default: message='same reading level'; break;
    }

    YAHOO.util.Dom.get(label_id).innerHTML = message;
      });
  return slider;
}