I remember visiting this website once...
It was called E! Online Smartphone Châu Âu
Here's some stuff I remembered seeing:
==> global assignment: ua=tool.device.ua [on line 28, column 3 in eprotoeu.mtiny.com/macros/utils.ftl]
in include "/includes/ua.ftl" [on line 256, column 9 in eprotoeu.mtiny.com/macros.def]
You can setup exception-handler for storefront in order to show a different page to customers if any errors occur.
Errors are also logged to the s2m.log file in storefront version folder.
Note that error details will not appear on live version of storefront.