My Adsense-supported website's error.log file has lots entries like this which I'm fairly sure are advert related:
[Fri Apr 12 07:19:57 2013] [error] [client IP] File does not exist: /var/www/[mywebsite]/htdocs/eyeblaster, referer: http://apac-bidder.mathtag.com/notify/iframe? [snip lots of junk]
What is it and is it harmful? Should I create an empty eyeblaster.html file to shut it up?
I also have another two that are like it - are they related?:
[Fri Apr 12 07:08:52 2013] [error] [client IP] File does not exist: /var/www/[mywebsite]/htdocs/7196176924447058959
[Fri Apr 12 07:13:58 2013] [error] [client IP] File does not exist: /var/www/[mywebsite]/htdocs/_sans
Take a look at StackOverflow question above - Determine which advertisement made a request to /eyeblaster/addineyev2.html. I think all will be revealed :).