What is the do you mean by "standard install page"?  The default Apache page, or FreeLSS?
The error you see above is saying that something is already running on port 80.  Either FreeLSS is already running, or you are already running something else on port 80.

I'm now at the stage of having compiled freelss and done all the setup (except maybe plan, haven't checked that yet) and get this when I log in via ssh:

Last login: Thu Nov 19 23:33:43 2015 from 192.168.0.71
Creating MMAL video mode camera resolution=1280x960
Creating callback data...
Creating camera...
mmal: mmal_vc_component_create: failed to create component 'vc.ril.camera' (1:ENOMEM)
mmal: mmal_component_create_core: could not create component 'vc.ril.camera' (1)
Creating Mock camera, width=1280, height=960
Reinitialized.
Running on port 80...
Exception: Error starting server on port 80
terminate called after throwing an instance of 'std::string'

The web server IS running and available on :80 - I get the standard install page.

I'd welcome any hints or tips on starting to troubleshoot and fix these issues.

One set forward........ :-)

Cheers