I'd like to, occasionally, tell Firefox to download the mobile version
of pages, instead of the normal page.

Reason is that sometimes I have to connect my laptop to my mobile phone
to get internet, and my data plan is limited to just 1 Gbyte/month. When
I browse a page directly using the phone I get, for some pages that have
it, a version with less graphics and simpler format, loading faster on
mobile phones.

So, when I'm tethered to my mobile phone I would like Firefox to request
those versions.

Is it possible?

Cheers / Saludos,

Carlos E. R.

(from 13.1 x86_64 "Bottle" (Minas Tirith))