on page 259 the css in slider.css goes like this:

Code:
span.sliderControl {
  display: block;
  height: 79px;
  position: relative;
}

span.sliderTrack {
  background: url(slider_scale.jpg);
  display: block;
  height: 72px;
  left: 0;
  position: absolute;
  top: 7px;
  width: 430px;
}

span.sliderControl span.sliderThumb {
  background-image: url(slider_thumb.gif);
  cursor: w-resize;
  height: 35px;
  position: absolute;
  top: 0;
  width: 20px;
}

span.sliderControl input.slider {
  margin-left: 430px;
}
and on page 258 the html goes like this:

Code:
       <label for="percent">Percentage
          <span class="sliderControl">
             <span class="sliderTrack"></span>
             <span class="sliderThumb"></span>
             <input id="percent" name="percent" class="slider from0 to100 scale4" type="text" value="0" />
          </span>
        </label>
Why is there in the css:

Code:
span.sliderControl span.sliderThumb
but only:

Code:
span.sliderTrack
??

Thanks