CSS-question concerning a PIER-image running on seasidehosting...

Dear all, first of all I have to admit that I obviously do not fully understand how PIER deals with external files. I’ve developed a (non-commercial) website which I want to run via www.seasidehosting.st – a really great service. I’ve added Randomizer to my website and it works with static files/resources that I’ve uploaded to the resources directory on the seasidehosting server. So far so good - but I still have a problem with a CSS-File that I have created for the website. In my development environment (on my computer) everything looks good. After uploading the image to the seasidehosting server some things (e.g. the main menu) looks very different. Obviously I didn’t “connect” my CSS-file correctly to the uploaded PIER-image. Do I have to apply the FileLibrary for getting the access to the CSS-file? Within the “setting”-area for the PIER-components only local files can be specified for the associated CSS-files. I’ve tried so many things up to now with no result – so I would be really grateful for any help in this matter. Many thanks in advance and best wishes Carl