Please try to execute rm $PIWIKDIR/tmp/assets/*.css on the command line in case you have access to the command line or delete this file manually on your webserver (there should be only one).

it might fix your problem but not sure. It doesn't return any response at all when requesting the CSS but still an HTTP 200. Can you access your server logs and have a look there?

Did you update via the UI or manually? Which PHP version are you using (if you know)?

File deleted, but nothing changed

sadly I do not have access to my server logs
I updated the software automatically, but the problem was there even with the previous version.. and php 5.4

Thanks for your time!

i tried to add the css with google chrome console and it worked.. so if you can tell me where to add manually css to all the pages it would be great!

It won't be possible to do it manually as the file would be overwritten. Without having access to the server logs it will be hard to tackle this issue. From which version did you update? Is it maybe possible that we get access to the server itself. If so, please send us an email to "hello at piwik.org" and comment here