error message

Anyone know what is causing this:

[Sun Nov 9 08:38:25 2003] [error] [client 81.6.245.147] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:37:36 2003] [error] [client 217.80.94.153] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:37:33 2003] [error] [client 217.80.94.153] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:37:32 2003] [error] [client 217.80.94.153] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:36:47 2003] [error] [client 68.85.75.99] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:36:42 2003] [error] [client 68.85.75.99] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:36:42 2003] [error] [client 68.85.75.99] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:35:57 2003] [error] [client 155.239.152.226] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:35:56 2003] [error] [client 155.239.152.226] File does not exist: /home/cherrycr/public_html/[F]
[Sun Nov 9 08:35:53 2003] [error] [client 155.239.152.226] File does not exist: /home/cherrycr/public_html/[F]

there are a bunch more that I didn't include - the IPs above all belong to ISPs - South Africa, London and US...

I feel like I should know what the [F] switch means, but I am drawing a blank and a quick search didn't uncover the answer.
(and I am quite sure this will be a total flat forehead {duh} headslap when I get the answer )

Thanks