Hi Everyone!
Bootstrap now has a new version (4). Colt teaches version 3 in this course, so please use the original documentation for version 3 and ensure that you're using version 3.3.7 in your code as you're following along with the lectures.
If you'd like to teach yourself bootstrap 4 (which should be very easy after finishing this section of the course) then checkout this migration guide.
You can also use this guide to upgrade your YelpCamp project (covered later in the course) from bootstrap 3 to version 4.
I personally recommend learning both versions as a lot of companies will still be using version 3 in their code and will need developers who know both versions to help them migrate.
Thanks,
Ian
Course TA