If i want to be expert on Wordpress or Joomla is it mandatory to know html,css and others systems? What’s the requirements before start learning Wordpress or Joomla?
Do you want to create your own Wordpress templates? Then you’ll need to know HTML and CSS.
Do you want to create your own Wordpress plugins? Then you’ll need to know PHP and probably MySQL.
Do you just want to install Wordpress sites, using templates and plugins made by others? Then you don’t need to know anything of the above.
You don’t need any specific skills to manage Wordpress, it has a lot of plugins that can help you with anything.
But to create plugins or themes yourself you’ll need basic HTML/CSS/PHP skills.