I am having trouble displaying a background image on a web page and have no clue what's wrong. I am sure it's something simple that I just don't see. Here is the code:

background-color: yellow;
/*does not work*/
background-image: url('../pictures/solidgreen.jpg');

/*moved jpg to root directory. does not work*/
background-image: url('solidgreen.jpg');

<div id="header">
<p>This text displays in the header</p>;

The solidgreen.jpg file is a test file I created thinking there might be something wrong with the jpg file I am trying to display. Nothing works.

Thanks for any suggestions or help with this simple, perplexing problem.