Thanks for your replies, great to hear your input and ideas.

We're on a linux server so that would rule out the windows server replying "none" for "file not found"

IP addresses are totally random and not our own, so thats another thing ruled out.

Here's an example of a line from the error log file, with the addresses taken out for privacy.

[Wed Jan 27 08:10:50 2010] [error] [client 00.00.00.00] File does not exist: /hsphere/local/home/username/domainname.co.uk/includes/templates/classic/css/none

Over 200 of our error entries show up this error every day.

Has anyone experienced this before?

Thanks for your help.