One page showing without loading theme

Hi

Our WordPress website was developed by someone who apparently used some non-standard code. Today I edited one page and when I saved it the page “lost its theme”. All the other pages are displaying correctly but that one page is just displaying a white background with black text, no images or anything.

It happened once before and I managed to fix it by changing a setting in the database. Now I can’t find that setting again. Is there someone who can point me in the right direction?

The page that isn’t working is at:
http://www.hosting101.co.za/web-hosting/

Thank you!