I pieced together these CSS and Javascript files through a lot of research on the Internet. I had never dealt with modals before, so it was a fun exercise in web coding; well, I enjoyed it, at least. It took awhile to get the opening of multiple modal files correct and allow an infinite amount to be created with both CSS and JS applied.
The main file; it's not large, but it sets up the website to load properly. Given that the main site is contained in one file, this is important.
Small file to control how the navigation links behave
Define how the modal buttons look on page
What happens to the modal and define how the visitor can exit the modal by selecting an 'X' to close or clicking outside the modal