Hi,
“What happens if the Applet visibility Type Is Null” is very common question which is has an answer in Bookshelf. I am just copied it below,
Visibility Settings
A view not set up with visibility settings (the properties Visibility Applet and Visibility Applet Type are
blank) means the following:
When navigating from another view to this view without visibility settings using the Show drop-down
list, the queries context and record focus are kept from the previous view, assuming that the same
business components and search specifications are relevant.
However, when navigating to a view without visibility settings using the Site Map or the Screen Tabs,
the view behaves as if the most restrictive visibility would apply to this view. (Normally this means
Personal or Sales Rep visibility, depending on the corresponding visibility settings of the business
component of the view’s Thread Applet property.)
Resource: Siebel 7.8 Bookshelf Object Type Reference Document, Page 306.
Regards.