When I add a Vyrso book to the cart using Firefox on my Samsung Galaxy Note 1, and then try to press the big green Place Order button at the bottom of the cart page, it doesn't press.
I can work around the issue by requesting desktop mode (through the menu), which gives me the same cart page as used on a PC, and then the smaller green Place Order button is pressable.
Not a big deal: just thought someone might like to know.
Firefox 23.0 (with Adblock Plus 2.3.2) on Android 4.1.2.