Hi,
thanks for your help.
i think the reason was the http-protocol 1.1. I have changed the command string in the monitoring tool from version 1.1 to 1.0 and all is fine. But i also removed the HEAD-Request with .htaccess custom code the same time. So i had to proof which setting it was.
The IPs of monitoring tools are in the whitelist, too. Now everything ist fine – the log doesn’t shows the 403-error anymore.
THX, nukleuz
Or do you think i have to change some of my settings i did?