Newbie mantenance page based on IP address

Simple enough, just use the "HTTP::status" command.

http://devcentral.f5.com/wiki/default.aspx/iRules/HTTP__status.html

Something like this would work. This is simply a different iRule "event" and can be inserted at the end of your current iRule.

when HTTP_RESPONSE {
   switch -glob [HTTP::status] {
             "403" -
             "404" - 
             "500" { HTTP::redirect "http://www.sample.com/maintenance.html" }
       }
 }

I've never used HTTP::redirect from the response event and I'm a bit confused that it's usable from there but give it a shot. If it doesn't work, use the rule below instead:

when HTTP_RESPONSE {
   switch -glob [HTTP::status] {
             "403" -
             "404" - 
             "500" { HTTP::respond 302 Location "http://www.sample.com/maintenance.html" }
       }
 }