I have a Wordpress theme and in one of the theme files I have put a link to an image file but unless I put an absolute link I am not sure how to link to it.

The file is at:

http://domain.org.uk/wp-content/them...mages/logo.jpg

The template file is at:

http://domain.org.uk/wp-content/them...ges/header.php

What should I put in the header.php file to display the image without using the http://domain.org.uk

Can I do a relative file path?

Thanks.

You can use /../ to go backwards a directory.

If you are putting this code into the php code directly you can use:
<img src="<?php echo bloginfo('template_directory') . '/images/yourimage.jpg';?>"
to sub the path files to your template. This is assuming you have a folder called "images" of course, etc.

Any method will output the full path to the browser anyway, so may as well hard code the FULL path if you are working live.

Good find!