On a PC:
C:\Program Files\Signal\web\
On a Mac:
Right-click on the Signal application bundle and select "Show Package
Contents", then /Contents/Resources/web/
Note that on the Mac this will break Signal's application signature
(because you're changing the contents of the application) and this
could cause problems accessing Signal if you have your Mac's firewall
enabled. I've added a crossdomain.xml file to the upcoming Signal 1.2
release so this won't be necessary in the future.
--
Matt Stevens
www.alloysoft.com