Where do i can write codes with Html and Css?

Question

Where do i can?

Answer 1

Open your profile and click on codes. Then select web language.
Or
On the app main page find a sector with { } symbol click on it you will see all codes for the day. Click and select web.

Web combines HTML, CSS and JS

Answer 2

Sololearn code playground as 🐱🐱🐱 suggested.