510 error

[acgodung]

I notice that every ~6 hours I will receive 510 error for a few minutes. It responses me like this

Not Extended

A mandatory extension policy in the request is not accepted by the server for this resource.
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Apache/2.2.8 (Fedora) Server at --Mysite's URL-- Port 80

I can't browse any pages at the time and receive this message instead. After that, It will work fine again.

What's wrong?

[admin]

This typically means that your site is exceeding the number of slots you are allowed for the domain name.  (Connection slots)


Please use the "Help Desk" link within the Plesk interface to have someone check this for you.

[acgodung]

Thank you for your respond, admin