I tried to give css property width in percentage , but i am not able to do that. Can anyone help me out with what is the correct procedure for dash-html-elments.
Applying CSS to Dash HTML Components should largely work the same as with vanilla HTML elements. You could try styling some plain HTML to sanity check that your CSS does what you think it should. Could you post a minimal example of the Dash code for us to see what exactly is going on?