How does the navbar-fixed-top in Bootstrap CSS cause a part of the container to be concealed?

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The navbar-fixed-top class in Bootstrap CSS fixes the navbar to the top of the viewport, making it remain in view even as the user scrolls down the page.

This can cause the content of the container to be concealed because the fixed navbar takes up space at the top of the viewport, effectively covering up that area of the container. To prevent this from happening, a margin can be added to the top of the container to ensure that the content starts below the fixed navbar.