Button in menu (mobile)

I used the css provided in the following link to create a button in the main menu. http://hellominti.com/forums/topic/how-to-add-button-in-menu-unicon/
The result is great on a laptop but on mobile devices the button goes funny. You can have a look at it here: http://www.fabienmathieudesign.com

Any idea how to fix that ?

Thanks

Ticket