PHP include not working?

Hey,

I can't seem to get my CSS working properly when I use PHP include for my header.

At the moment, my header file (header.php) contains my CSS file, which contains styles for all my pages:

<link rel="stylesheet" type="text/css" href="css/style.css" media="screen">

and a logo.

In my index.php file I have 3 divs underneath the logo, which have background images and are my main navigation to the other pages on my site.

basically, if I include my header.php file at the top of my index.php file :

<?php include("inc/header.php"); ?>

when I load the site, my background texture and logo are styled correctly, but the rest of the page is blank. Which makes me think that the CSS is only being applied the the elements directly within the header.php file, and not to index.php. Have I just made a mistake somewhere?

oh and, my site directory looks like this:

• index.php
• css/style.css
• inc/header.php
• img/img_1.png img_2.png img_3.png

and in my CSS all my background images are referenced as:

background-image: url("../img/img_[number].png");

hope this makes sense! and thanks :)