Blank PHP pages after CHmod

I am getting Blank pages when calling on index.php of the advanced guestbook. This was after going exactly what was said on the templates page by changing the permissions.

However when going to admin.php, it works fine. If I reduced the permissions from 777 downwards I get forbiddon 403 errors

Anyone any ideas? (I have tried twice and both installs are unusable.)

wsftp did not change permissions although log disagrees.

CPanel file manager made the guestbook work despite puttin gin exactly the same file permissions.

Think I have learned something today.