Hi,

is it a standard installation of a default template? For example Corporate site or have you created your own site.

According to your description it seems that you configured security checking on your site. For example Requires authentication in the CMS Desk - Properties of document- Security tab.

As a test you can disable security check for images. In the Site Manager - Setting - File you can uncheck option Check files permissions. Where are you storing files? In the database or file system? You can find your configuration in the same section as was described above.

As for changing the web.config file. What exactly have you tried to configure?

Thank you.

Bset regards,
Ivana Tomanickova

As for the Design tab. Have you logged in as a global administrator?