Document from another domain?

I don’t understand the issue with a document from another domain as everything is on my development box.

Can this be caused by the CodeIgniter framework?

I am simply trying to duplicate the example supplied with the download which has the tab bar on the left and an iframe on the right which loads a file with two drag and drop trees.

The problem may occur if one of iframes loaded with different domain in URL, it doesn’t matter that urls may reffer to the same box.
For example if you loading page by local api
and some iframe inside it uses
It will be counted as different domains