Possible CSS error in connection with WP dashboard

Hello,

when I activate the plugin in my WP installation (actual version, Multiuser), the font in the dashboard changes to the pure definition “Sans-Serif” – the font normally used in the dashboard by WP is overwritten. That doesn’t have to be.

The problem seems to be following line in /admin/css/style.css:

body {
    font-family: sans-serif;
}

After deleting these three lines all seems to be right without any glitches anywhere.

Regards,
Besim