CSS+HTML doesn't work

[AAstroPhysiC]

Hi,

Firstly Hi to anyone who's reading this. I am new at this forum. I am also a beginner in HTML+CSS. So you know i just wanted to make my own website via Atom. But you know I don't know how i am gonna make the connection between CSS+HTML. For example when i put a <div class="header" to h1, it should be able to change the color on CSS. But it isn't doing that. I also put the <link command into html.

The code which i did put:

I dont get it.

Thanks,

[joaojotta]

Is this really an Atom question? (have you linked your CSS file in the HTML header?)