When you log into Cerb from Safari Mobile on an iPhone, you’ll be given the option to switch to the mobile interface.
Tap the Switch to mobile button.
You can then save a shortcut to Cerb by tapping on the Share icon in the middle of the bottom toolbar:
Tap the Add to Home Screen option:
Change the name to Cerb and tap the blue Add action in the top right.
You now have a Cerb app icon:
The first time you open Cerb using the new icon you'll need to log in again, since cookies aren't shared between Safari Mobile and website shortcuts.