How do I connect my html and css codes so they can be read by web browser?

Question

I have created f.HTML and write f in h1 inside div.
so I have created f.CSS and write to make a box with round corner. and in HTML in head I write
<link type="text/css" rel="stylesheet"
href="f.css"/> and run it shows only f . saved and refresh again only f..

Answer 1

ok, first of all, do you write your HTML/CSS on Code Playground or your local computer?

Answer 2

Verify that you put the link tag inside your head tag. Verify also that your css file is in the same folder as your html one

Answer 3

Read by your own browsers only or read by everyone browsers?