Joomla website - content displays for registered users but not for regular visitors

I have to do fix some bugs on开发者_JAVA百科 a Joomla website that I didn't build. Also, I don't know Joomla. Biggest issue at the moment is that the content displays for registered users but not for regular visitors. The website in question is http://johngilesfoundation.com/

Can anyone help?

It will be nearly impossible to say definitely without knowing what is supposed to display, and what is actually displaying and the extensions that are installed. Joomla 1.5 has a rudimentary access control that could be your issue. In virtually everything - menus, modules, articles, etc - you have the ability to set the Access Level. It is usually on the left side of the details page and the options should be Public, Registered, and Special. Make sure that all of these are set to public.