First, why are you emitting all this crud from a Servlet rather than using a JSP.
Secondly, you are using a protocol.
"C:/../calendar.css" will not work ever. First of all, you can't use file protocols on the web and expect things to work on any system other than your own. Do you really think that everyone using your app is going to have your files on their systems? Moreover, that's not even a valid file URL.
See the JspFaq (the entry named ResourceUrlProblems) and modify your resource URLs to use server-relative URLs that begin with the context path.