Just as it says, when editing a mobile CSS file, like wireless.css, from within the admin panel the preview is still the full-sized window.
Honestly, is there a point to CSS like wireless.css? Most of the classes are duplicated in the variant index_variant.css files for the default themes, and in other first party (made by our favorite Elkarte devs like
@Spuds ) themes.
IIRC wireless is just a remnant.
I'm not even sure it's actually loaded anywhere.
ETA: and yes, it was removed a while ago in 1.1.
Cool, then I'll close this. No need to worry.