https://medium.freecodecamp.org/how-to-keep-your-footer-where-it-belongs-59c6aa05c59c

A footer is the last element on the page. At a minimum it is at the bottom of the viewport, or lower if the page content is taller than the viewport. Simple, right? ?

When working with dynamic content that includes a footer, a problem sometimes occurs where the content on a page is not enough to fill it. The footer, rather than staying at the bottom of the page where we would want it to stay, rises up and leaves a blank space beneath it.