In weblinks hook_help the main weblinks.css file is linked for all pages with path 'weblinks' or 'weblinks/%'. Whilst this works (for now) it is not the proper use of that function - see our discussion at https://www.drupal.org/node/2457353#comment-9748641

It would be useful to review how we add .css files, in the main code and in admin.inc and the sub-modules, so that a consistent drupal-approved method is used.