How this web works

Hello everyone I am new in this website I want to learn the Responsive Web Design however I did not arrive to understand how this web work, how to learn a chapter and validate it because when I run my test nothing do not come and when I go back to continue they said I did not validate the first one please explain me how to test and how to move on

Best Wishes

Not sure I understand you, but if you are having issues running the tests on the challenges it might be a browser issue. You should use Chrome or Firefox for the curriculum.

If that isn’t the problem can you try to explain again what and where you are having problems.

<!DOCTYPE HTML>
<HTML>
    <Head>
        <Title>My FirstProgram</Title>           
    </Head>
    <Body>
        <h1>Hello World</h1>
        <h2>CatPhotoApp</h2>
    </Body>
</HTML>

the question is to display Hello World and CatPhotoApp and after I done it I tried to run it but I could not validate it in Curriculum

What is the url of the challenge you are trying to pass?

Remove everything except the h1 and h2 elements.

I assume you are on this challenge?
https://learn.freecodecamp.org/responsive-web-design/basic-html-and-html5/headline-with-the-h2-element/

thank you and the other problem was my browser I just installed Mozilla Firefox everything working properly