Before 8.5.3 local web preview often didn’t work for a number of reasons. Skype blocking port 80,
HTTP Server: Error – Unable to Bind port 80, port may be in use or user needs net_privaddr error
Or some other problem. Now your problems is solved, just open preference -> Domino Designer and change the port to a higher port i.e. 5000.
Fredrik, do you know a work around to have some level of authentication when web preview an xpage. Any help will be appreciate it.