To install SyncTERM as the default rlogin and telnet handler for Mozilla,
type in the URL "about:config"

In the screen that comes up, right-click, New->Boolean
network.protocol-handler.external.telnet = true
network.protocol-handler.external.rlogin = true

Then, right-click, New->String
network.protocol-handler.app.telnet = /path/to/syncterm
network.protocol-handler.app.rlogin = /path/to/syncterm