Website address / WordPress address killed site in progress

I am redesigning my website on http://www.robcoers.nl/wp while the root-site is still active.
In this wp folder i have been fiddling in Settings > General > WordPress address and also Website address… At first i shortened the website address till the root, but when i found out that didn’t work, i switched back to the original settings. Both were and are still http://www.robcoers.nl/wp

BUT … now this URL is corrupt. Site looks horrific and i can’t login to the wp-admin.

Watch the video: http://screencast.com/t/Q0b8xZ6t5Wsr

Please, help me out…
Rob