A box shadow puts a shadow under elements to make it look as if they are raised above the rest of the page.  Open folders.html from and save it as boxshadow.html.  Add a style attribute to the opening video tag so that it looks like this:

<video style="box-shadow: 10px 5px 3px 5px rgb(150,150,0);" width="640" height="360" controls>

When you try it the video should now have a grey shadow around it.  The values in the style are:

  1. the amount the shadow position differs from the element horizontally (10px)
  2. the amount the shadow position differs from the element vertically (5px)
  3. the blur distance at the edge of the shadow (3px)
  4. the difference in the size of the shadow compared to the element (5px bigger)
  5. the colour (grey)

Try different values to see what each one does.  Conceptually it is creating a ghost element underneath the real element.