[stevehb]

It looks like use them for CSS properties. The background for the outer div is set to #4e6590, the blue background. The background-image of the inner div (and its ::before and ::after) draw the parts of the zipper.

For example, the inner div has background-image of

    linear-gradient(to top, transparent 10px, #aaa 10px, #aaa 15px, #ccc 15px, #ccc 30px, transparent 30px), repeating-linear-gradient(to bottom, transparent, transparent 5px, #ddd 5px, #ddd 10px), repeating-linear-gradient(to bottom, #ccc, #ccc 5px, transparent 5px, transparent 10px);

which draws the teeth of the zipper.