strange hidden characters at the end of css files Follow

Hello,

after some time working with css files in Phpstorm 9.0.2 and including them with the link tag,
i get hidden characters at the end of a css file. i can only see them in the browser view source (added screenshot)



i tried everything, creating new css files and importing the content there, works for some time.
The problem only appears when i include them with <link rel="stylesheet" href="css/style.css">
when i write the css direct to the html there is no problem with the exact same css content.
i develop on kubuntu 14.04 with vagrant and nginx 1.8.0 as the web server and the css file is saved as utf-8.

Any Ideas what the problem might be?

Thanks in advance.