What are the constraints around the “url” parameter?

I've found that the grid will populate with items in the modern browsers when I have the url parameter set to localhost:8080 –

Grid at location: http://localhost:8080/app1/grid

URL parameter: http://localhost:8080/app2/items

However, when I deploy to my Dev system, and I use the name of that machine, the grid no longer populates –

Grid at location: http://my.machine.net:8080/app1/grid

URL parameter: http://my.machine.net:8080/app2/items

Same machine. Same domain. Same port. No grid items..

Thanks!

It looks like this is a SSL to non-SSL issue which still causes a cross domain Ajax call even though they are on the same server. Now, does the URL paramter allow for https connections?