I'm not sure why some are not seeing the problem you are reporting, as I certainly see it! Note that the home page looks fine, and the CSS is fine, but clicking another link (for instance, the "news" page) shows the problem.
This is likely the result of the "SEF" url settings, and there is a known issue with later Joomla! versions in the DreamHost environment (and there are several posts about this in these forums).
The "short" version with regards to solving this is that you should log into the Joomla! administrator back-end as a super-administrator and, in the global configuration settings, either:
1) Turn off SEF urls altogether OR
2) Turn on the "apache" SEF setting and rename htaccess.txt in your main Joomla! directory to ".htaccess".
Either of these methods will resolve the url re-writing issue that is causing the CSS files to be "not found".
Additional info cam be found here:
--DreamHost Tech Support