It looks as if there is a problem with the URL for logging in to a database via WebDirect.
In these circumstances:
opening a database running in FMS14.0.3,
hosted on OS X 10.10,
using a URL that includes a custom homepage URL,
with a target database name that appears with its .fmp12 extension.
Then WebDirect goes straight to the custom home page.
For several years FileMaker seems to have been pretty neutral about whether or not a FileMaker extension is included in a database name. So, if the extension is no longer permitted, I’d expect the WebDirect user guide to say so, but it doesn’t.