dle timeout checks traffic, keepalive timeout checks availability.
This question was asked and answered here: http://forum.mikrotik.com/t/explanation-idle-timeout-keepalive-timeout/3282/1
Keepalive timeout for authorized HotSpot clients. Used to detect, that the computer of the client is alive and reachable. User is logged out, when timeout value is reached
source: http://wiki.mikrotik.com/wiki/Manual:IP/Hotspot/User
Maximal period of inactivity for authorized HotSpot clients. Timer is counting, when there is no traffic coming from that client and going through the router, for example computer is switched off. User is logged out, dropped of the host list, the address used by the user is freed, when timeout is reached.
source: http://wiki.mikrotik.com/wiki/Manual:IP/Hotspot/User
status-autorefresh - WWW status page autorefresh time
Source: http://wiki.mikrotik.com/wiki/Manual:IP/Hotspot/User