Unable to open sites with HTTPS when connected through OpenVPN

I ran openvpn client on my Ubuntu 14.04 successfully, but the sites with https (SSL protocol) cannot be opened while http sites seems working fine.

Since OpenVPN works at the network layer and is thus independent of ports (i.e. port 80 http vs. port 443 https) it is more probable that https is blocked by your OpenVPN endpoint. But please make sure that it is really the same host you try with http and https.