automatic form completion

This question concerns the safe zone available under the additional protection options.

I have automatic form completion turned off in normal use and have unticked the ‘remember me’ boxes on the websites concerned.

I have cleared the safe zone browser of everything.

Yet when I log on to certain sites (banks) the username is automatically offered.

How do I

  1. Remove knowledge of these names from the computer

  2. Prevent the safe zone browser recording them or offering them in future.

Surely this action by the safe zone browser makes it less safe than normal?