In your logfiles, you get errors like this:
[Fri Mar 07 11:35:28 2014] [error] [client 192.168.0.2] client denied by server configuration: /var/www/data/htaccesstest.txt 2013-12-19 18:42:39 ::1 GET /data/htaccesstest.txt - 80 - ::1 - 404 0 2 2 6444#0: *11 access forbidden by rule, client: 192.168.0.30, server: , request: " GET /data/htaccesstest.txt HTTP/1.0", host: "192.168.0.30:XXXX"
Just ignore these errors. They are a byproduct of a check ownCloud needs to perform to make sure your data is secured.
The request to the htaccesstest.txt is us used to check if your /data folder is protected correctly to not allow direct access to files in it. For this test the following function is used: