Manual:$wgAllowUserCssPrefs

Security: $wgAllowUserCssPrefs
Allow user preferences implemented in CSS.
Introduced in version:1.17.0 (r63707)
Removed in version:still in use
Allowed values:(boolean)
Default value:true

Details edit

Whether to allow user-preferences implemented in CSS. This allows users to customise the site appearance to a greater degree; disabling it will improve page load times.