That I think is fine. The Terms of Service will explain everything for you. I didn't read it, but I'm just remembering from what I've read. You'll just need to watch your bandwidth if a lot of people visit your MySpace a month. Someone else wiill be able to correct me if I am wrong.
Also, if it's just for CSS, I'm pretty sure you can store the CSS file on MySpace servers, though I don't go to that site as I'm not a fan of social networking sites.