Resize a div element to its background image size

Question

Is it possible to make a

adapt to its background image? I mean to maintain the proportions width and height.

Clarification:

Answer 1

The easiest thing to do that doesn't need any javascript is to set your image as the background image and then make a .gif or a .png of the same size that you set as an overlay image in that div. That transparent .png or .gif will size the div. Transparent .png or .gif are only a couple of KB and your page will complete loading faster than with javascript.