I'm looking at your site now.
Whenever there is an error loading the assigned skin it falls back to a known skin otherwise the site would just not work at all.
Can you tell me the name of the skin you are using? Is it a custom skin or one of the included ones?
Right now it throws an error form the css handler. If you login to your site, then look for the administration link at the bottom, click it and go to site settings and see what skin is selected and try selecting a different one and save.
Also you can find out the error detail for me by going to administration then system log, and look for the errors at the bottom of the log as those are the new ones, there will be lots of junnk errors at the top that always happen on a new installation until the setup runs there ar eno tables so it logs a bunch of errors about that.
You could also download the log file from /Data/currentlog.config using ftp
Hope it helps,