jvoldby

Thanks!

It was in line 163 and 188 in nextgen-gallery -> lib -> core.php

Thanks, but what file is that in?

I think the answer to your question is finally here :-):
https://blog.ffff.ca/2008/12/28/changing-default-link-target-in-wordpress/

In WordPress v2.8 the link.js file is in the wp-includes/js/tinymce/theme/advanced/js directory.