Using Bootstrap?
Most likely.
Wanna apply some special rules to an element inside a grid (col-*) system within a viewport that satisfies something less than col-md but more than col-sm?
@media screen and (max-width: 767px) may be your friend.
If there is only one thing to come out of this, obviously the number 767.
This, to remind my future self.
Cheers,
somewhere between Dev & Ops 