This look not so good in the new mobile navigation. There is an vertical scroll bar.
Seems to have been restored at 17:48 UTC, January 23. See here more information: What happened to the top bar and it's restored now on meta.SE
Quoting from the accepted answer by Shog9:
There's a project underway to bring the mobile theme more inline with the design of the full site, including the new top bar and some experiments with vertical navigation that haven't been fully realized yet.
This... Clearly needs a bit more time to bake, so we've reverted the change pending further testing. We'll make a full announcement when/if this goes live again, but not until reviewing all the bugs already reported today under mobile-web.