We have a gateway Mikrotik router. Is there a way to redirect all http requests and display:
FIBER CUT, Please stand by…
That’s a bad day right there. 
You should be able to make hotspot do what you need to do. The first time you enable hotspot, the html files for it are created in the file store. You can just edit the login.html file to say what you need. If I remember correctly, you can also strip out the actual login prompt so they can’t sit there trying to authenticate.
http://wiki.mikrotik.com/wiki/Manual:Hotspot_Introduction
http://wiki.mikrotik.com/wiki/Manual:Customizing_Hotspot
That’s a bad day right there. >
Its ugly…