Thank you for the response.

So, I will start from the beginning.
I installed it successfully some time ago but...
One time I have noticed some problems with updating repositories and I decided to remove (through apt-get autoremove) three packages - Coderus's trusted repo, rzr's repo and n9repomirror.
The problem didn't solved so I removed also next two files from /etc/apt/sources.list.d/ : home-rzr-harmattan(...).list and n9repomirror.list .
After that the problem disappeared.
Next, I have installed again rzr's repo and n9repomirror without problems but Coderus's repository couldn't install.

To be honest, now I am not sure if that repository is still active.
How can I check it?