Tried the software for some days, but cannot find the solution to protect one or more folders

I use a lot of websites with each another password.

Is it possible to create a field, to let visitors not see the content, while I can using a specified key ?

With AllMyNotes you can protect one or more folders, and, also, whole database.

To protect whole database use menu item File -> Set Password.

To protect a folder, do right click on it in the left-hand Outliner tree view and select menu item Properties -> Set Password.

Regarding protection part of a text, I know what you mean (seen it somewhere), but yet we do not have this feature.