I want to make a website for someone i will make it in html and css but after i finish the site ,he wants to change the content of the site(update),like add images and add new paraghaps headers,,... how can i do that?

Something like he logs in and he can change headers,paragraph ...add image himself whiout knowing html 

Sry for my bad english

I found out what i need ....CMS and i need to learn php :))