Midori won't open some websites because of security certificate problems

At some websites i get the message:
Error granting trust: Couldn't find a place to store the imported certificate
pkcs11:library-description=PKCS%2311%20Kit%20Trust%20Module

In the Midori FAQ the problem is addressed as follows:
No key store is available or it's incorrectly setup. By default GNOME keyring can do this. Under Xfce it is recommended to enable “GNOME services” under “Session and Startup settings”. To make sure, that the output of “gnome-keyring –startup” is correctly sent to the environment, you can add “export `gnome-keyring-daemon –start`” to .xinitrc.

I don't have the file .xinitrc, and creating it in the home folder didn't change anything.
But then I found the package libp11-kit-gnome-keyring in Synaptic and it helped. Now i can access sites i couldn't (each time after confirming twice that i know the risk). But when i enable Javascript on those sites, they disappear and the message is:
pkcs11:library-manufacturer=GNOME%20Keyring , pkcs11:library-description=PKCS%2311%20Kit%20Trust%20Module
This has also happened at Trisquel wiki pages. It always happens at certain sites of www.verdi.de (second biggest labour union of germany).