You don't have permission to access /update.php on this server.

[Mikaelft]

I am admin on my photo gallery, but I get this message:
You don't have permission to access /update.php on this server.

[Joe Carver]

If you are seeing an error message without a way to log in, then see the docs:

Authorization check

Look for the bullet / section: "If everything else fails". Follow those instructions.

[Αndré]

This seems to be an error message of your web server, not a message from Coppermine, right? Please attach a screen-shot.