Thank you for your post.
Using your sample link above, I entered this into Safari 8.0.6 under Mac OS X 10.10.3, but that server cannot be found. Also, in your example, you are showing two different servers. Remember that a custom homepage must be placed in the web server's root folder. This folder is on the machine in your FileMaker Server deployment where the web server is running.
Feel free to send me a private message with the actual details so I can test it here.
Thanks for your testing a few weeks ago. We figured out that something was wrong in the web page that was sending the link to Safari. It is working as expected.