Strangely I am getting hundreds of these errors a day:
[error] [client XXX.XXX.XXX.XXX] File does not exist: /var/www/website.com/web/error/404.html, referer: http://www.website.com/userinfo.php?uid=188
[error] [client XXX.XXX.XXX.XXX] File does not exist: /var/www/website.com/web/SPA/jseffects
Also there are these errors which are less common:
[warn] (103)Software caused connection abort: mod_fcgid: ap_pass_brigade failed in handle_request function
The "File Does Not Exist" errors are happening to all my sites.