This is the message I will receive when I trying to create a new page, but unfortunately the page's name is same as one of my child portal's name.
"There is a site domain identical to your page path"
The message only shows about couple seconds and then phased out, it took me couple times to re-try and saw the same message couple times to figure out why I couldn't create a new page.
More user friendly messages, such as: Your page name should NOT be same as your portal name. Page is not created. blah, blah...