[Typo3] Website Access Error Message

[Friedrich Schick]

Hey,

Problem:   I have some content, which should only be accessable to 
logged-on users
(on my website). Furthermore i want to link on public pages to that 
content.

Behaviour:   Typo3 (3.7) behaves as it should. Logged-on users can see 
the content,
not-logged-on users don't.

Question:   Is there a way that every user, which has not logged-on gets 
redirected to
a general page (which tells the user to login) or pops-up an error 
message (you are
not logged-in)?

My idea:   A little php script should check if the userid exists, if so 
everything is ok, else
redircet the user to a specific page on the website.

Any suggestions?

Cheers,

Schick