My header is not fitting properly on the top of web page?

Question

I'm a beginner and I'm trying to fit my header on the top but it's not fitting. Here is screenshot:

Here is my source code:

<header style="height: 50px;background-color: rgb(26, 26, 26);">
    <div class="container"></div>
</header>

Can you please let me know, What's wrong here? Help would be appreciated.

Answer 1

You need to add the following style in your css. There is default styles of browser which needs to overridden, in order to achieve the requirement.

html, body {
    margin : 0;
    padding : 0;
}