If I start a another browser, go to the challenge url without signing-in (like a new user), and start coding in the index.html and styles.css files, then my link element will look like that below.
However, if you create the project files (html & css) in an IDE like (vscode, pycharm, etc.) you will be able to choose where the css file is
located relative to the html file. Some developers like to keep their css files in a folder called css, for instance.
If you were to copy your html and css code from your IDE and paste them into the official freecodecamp challenge page, there will be a problem since the freecodecamp server doesn’t know where the location specified in the href attribute is on it’s server.
There is a good explanation for Absolute and Relative urls on the mdn website, where there is a wealth of other information regarding web development.
If, however, you would like to simply carry on with your challenge, you could test your that your link element is coded properly by assigning some styling to the universal selector like this:
* {
background: red;
}
If that turns the preview background red then you know that the link element has the href attribute set correctly. If so, your navbar selector is not coded correctly.