I upgraded from a 9.10.x install and had the following in that field:
Code:
http://download.freenas.org/jails/9.3/x64
I was having problems creating jails so I changed it to:
Code:
http://download.freenas.org/jails/11/x64
I was then able to install jails without errors. Of course, this could have been completely coincidental (and wrong) but I was just wondering what the default state should be.