ERR_EMPTY_RESPON

Hi,

i set up a new Server.
Domains and IP's are routed correctly.
But if i open Domain, theres nothing. NO default Page of the Websites.
After i installed Plesk, i removed nginx. Is this something which caused this Problem?
Ping to Domains are fine.

Error:
--------
Die Seite yourdomain.de funktioniert nicht
your.domain.de hat keine Daten gesendet.

ERR_EMPTY_RESPONSE
--------

The Backend, Plesk Login, Hostname is fine.
The Webserver Trouble...

ERR_EMPTY_RESPON