There are files missing from your server. Did you look at the error
messages in the Javascript Console?
Neither jQuery nor jQuery UI JS and jQuery UI CSS were found at
the locations you tried to load them from on your server.
This is not what is causing your problem, though, because the
image you showed above clearly shows that there is at least SOME
kind of CSS loading. I see none. You must have two different
websites set-up, or else something changed between the time that you
captured that image and now.
You need to fix that first.
BTW, XHTML is obsolete. Nobody uses it any more. Unless you're
doing government work. ;)
for some reason when
I'm in preview mode I'm able to see the tabs
What
is "preview mode"? Are you working in some IDE? Use a real
browser to test. Chrome has the best development tools, but, of
course, you should test in the most popular browsers you expect your
users to use.