This layer has id="scrolled".
Make sure it has following CSS properties set up:
* position (absolute or relative)
* width and height
* clip.

You must also create elements with following "id" attributes:
* scrollup [here: blue box]
* scrolldown [red box]
* scrollbar. [white box]

Each one must have position, width and height set up. You can customize their look with CSS and even use images.