[Sat Oct 20 15:34:49 2007] [error] [client IP] File does not exist: /var/www/vhosts/mywebsite.com/httpdocs/mywebpage.html/robots.txt

This line is a bit odd, as it indicates you may either have a problem in one of the virtual hosts on your server, or a bad link somewhere. Robots, on their own, won't look for a robots.txt file anywhere on a server except in the root directory, so the only way this request would occur is if you have a link to robots.txt somewhere that is incorrect, or if one of the virtual hosts is configured incorrectly.

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