Just CSS. Absolutely NO jQuery/javascript or any other programming language and no images.

This is a single empty <div id="mondrian"></div> with all the content generated using just CSS.

It demonstrates a method of using multiple linear-gradients to produce lines and solid color areas using percentage sizes and positions.

Just remember that the first linear-gradient appears on top, and further linear gradients are stacked under each other.

The apparent border is produced using an off-white border and two box-shadows.

Update - Animation added to the artwork to show the construction. This does not alter the fact that this uses just a single empty div.

The stylesheet for this demonstration is in the page head, but if you use this, please keep my copyright comment with the stylesheet.