Chapter 1 What’s New for FortiOS 5.2.1 : Wireless Networking : Captive Portal for WiFi : New Configuration Options
  
New Configuration Options
The following options can now be configured for captive portals that use wireless interfaces:
Security exempt list names can be added to a captive portal. This option is only available when user groups are selected as part of the SSID configuration, rather than being a match for groups in the security policy.
URL redirection is available after the disclaimer/authentication screen.
Four types of portals are available: authentication, authentication with disclaimer, disclaimer only, or email collection. When the mode is email collection or disclaimer only, the options for setting user groups or having an external captive portal are not available.
Syntax
config wireless-controller vap
edit <name>
set security captive-portal
set portal type {auth | auth+disclaimer | disclaimer | email-collect}
set security-exempt-list <name of list>
end
end