changed the WordPress address (URL) by accident

Your blog is not ruined, just because you changed the URL, the CSS is not found, and the styling is wrong…
You must go to the adress http://yourblogname/TheWPInstallFolder/wp-admin

where TheWpInstallFolder, is the name of the subfolder you installed wordpress in ..

check again your install dir name(caps and all) , because apart from missing CSS and theme file, your blog works fine (including embaded videos etc..)
anotehr question, where and how did you changed your blog URL ?

If you changed that address in the wordpress admin/settings area, then see the video below for how to correct the problem.

http://educhalk.org/blog/?p=21