Bootstrap 3 navbar doesn't work anymore
问题 Well... yesterday it worked, tomorrow dont... it's true! On console it gives this message: Error: Bootstrap dropdown require Popper.js (https://popper.js.org) The page is loaded but the navbar doesn't look liked it should do: the voices are aligned in vertical instead that in horizontal (so I have many columns). I see bootstrap 4 is finally out... but I would prefere to not pass at the new version. In my html I use: <link href='http://getbootstrap.com/dist/css/bootstrap.min.css' rel=