I can simply press 'X' and the banner goes away.
Correction: it goes away on my phone only. On a full-fledged web browser, it does not fully go away.
However, on
www.battlemaster.org it hides the bottom status bar, but on m.battlemaster.org (even if you're not on a phone you can use it) it does not hide the status bar, although it's still annoyingly present.
