WPDM plugin with more than 200 errors.. FIX?

Hello I recently installed the plugin WP Download Manager for my site. After some graphical issues I checked the CSS and noticed that there are multiple errors.

I can not explain myself why there are so many errors in the CSS, because the syntax looks correct for me.

http://jigsaw.w3.org/css-validator/validator?uri=http%3A%2F%2Fvocaloid.de%2FWordpress%2F&profile=css3&warning=no&lang=de&vextwarning=true