Webconverger has its own Firefox kiosk extension to tweak the user interface elements such as the URL bar and icons.
The goal with this default to have a stable, simple & familiar user interface for using the Web.
No address bar
Customization option, perfect for filtered setups. For customers who want patrons to browse, but not enter in URLs to navigate away.
Neon has further tweaks and currently proprietary extension for the digital signage use case.
If you're concerned about the scroll bar, alter the overflow CSS element.