You have bootstrap 3 and 4. Just pick one version to use. If not, things may look odd on different browsers. It seems the Bootstrap syntax you are using is Bootstrap 3, so I would go with it for now. Also, you only need one Bootstrap 3. You have two different versions of Bootstrap 3. Finally, you have animate.js in your external files, but I can not see where you are using it. Always make sure you are never loading extra libraries which you are not using, because it potentially slows down the page loading time.