I got my free ssl at startssl.com and it works really fine. My site is working with https://. After I configure LAMP and VSFTP and broke something in there, I decided to re-install UBUNTU 12.04 OS to wipe out all the configurations and unnecessary thing i made in there.
Following the same procedure as I was configuring it before and added the same
When I restart the apache2 it showed FAILED instead of OK. I immediately run this command cat /var/log/apache2/error.log and found out the error Failed to configure CA certificate chain!.
I followed this post http://serverfault.com/questions/228485/failed-to-configure-ca-certificate-chain but still no luck.
BTW, I configured my VPS like this tutorial https://www.digitalocean.com/community/articles/how-to-set-up-apache-with-a-free-signed-ssl-certificate-on-a-vps and it works so fine before i re-install my OS.
These answers are provided by our Community. If you find them useful, show some love by clicking the heart.
If you run into issues leave a comment, or add your own answer to help others.