Rated 3 out of 5 stars

If your going to split the main interface, make it as simple as possible.

Keep the main URL bar where it is along with links, and just have a panel for the seperate web page/pages only.
It gives more space for the web page to display.
Basically just put a small bar down the middle. Done.

This review is for a previous version of the add-on (0.8.8).