[Seaside] FileLibrary - how to update stylesCss?

[itsme213]

I have MyFileLibrary and imported a regular styles.css file into it, so I 
now have a method #stylesCss.

In my specialized session class I do:
updateRoot: anHtmlRoot
 super updateRoot: anHtmlRoot.
 anHtmlRoot stylesheet
  url: MyFileLibrary / #stylesCss.

But now when I change the string in my #stylesCss method the new styles do 
not seem to reach the browser (after browser cache clear etc.) Is there 
something special I need to do? I'm not using Apache or anything fancy, just 
straight served from Squeak (WAKom I think).

Thanks - Sophie