How do i create backend Content Management Portal?

I build most of my sites without using Wordpress, Joomala, etc. I'm strictly an HTML and CSS coder. A few of the sites I've built have small sections of content that need to be updated on a regular basis and I'm interested in creating a simplified backend content management system to make these changes.

Is there any systems available that allow you to add CSM capabilities to a standard HTML website?

If web development is just you do for fun then use an open source CMS. If you are serious then write your own CMS that meets your specific requirements.

Writing your own CMS will also help you in constantly expanding your web base and improvise programming skills.