It means that a file requested from the server is not found...yes it is obscure, but that's what it is...
To fix, and also so that Netscape browsers won't fail miserably reading your pages, grab the file from:
And copy it to \screensurfer\hostserver\docs
You apparently have downloaded one of the later builds of 2.0.4, which we are about to go general availability on; the surfer.css file is part of the extended attributes support in Screensurfer which has been implemented for baseline stylesheet capable browsers (NS4+ and IE4+). Sorry for the confusion...