linier i loggen - hvad er det?

nogen der har en idé om hvad det lige er for en slags trafik?

[Mon Jun 07 12:47:33 2004] [error] [client 66.237.60.72] File does not exist: /web/riversen.dk/robots.txt
[Mon Jun 07 20:57:27 2004] [error] [client 66.196.90.162] File does not exist: /web/riversen.dk/robots.txt
[Tue Jun 08 00:20:33 2004] [error] [client 65.54.164.98] File does not exist: /web/riversen.dk/robots.txt
[Tue Jun 08 01:29:23 2004] [error] [client 24.97.214.154] File does not exist: /web/riversen.dk/robots.txt
[Tue Jun 08 03:23:33 2004] [error] [client 65.54.164.96] File does not exist: /web/riversen.dk/robots.txt
[Tue Jun 08 10:26:33 2004] [error] [client 66.196.90.162] File does not exist: /web/riversen.dk/robots.txt