I am running ddclient in raspbian and the IP is also updated in DYNU panel. I have also set up cronjob as mentioned in one of the articles in this website.

However the domain name is not opening up my local website. The local website is running fine in my raspbian.

I have allowed all http and dns traffic to the raspbian local ip, in my router. However the website http://mydomain.com simply doesn't load up ever. Please guide.

DDClient updates your IP correctly is not the only thing needed for your website to be accessible though it is necessary. Is port 80 open on the website's IP? Use this port check tool. Many ISPs are known to block port 80.