Bootstrap 3 for Sass is a Sass-powered version of Bootstrap 3, ready to drop right into your Sass powered applications. This is Bootstrap 3. For Bootstrap 4 use the Bootstrap rubygem if you use Ruby, and the main repo otherwise. Get the lowdown on the key pieces of Bootstrap's infrastructure, including our approach to better, faster, stronger web development. Bootstrap makes use of certain HTML elements and CSS properties that require the use of the HTML5 doctype. Include it at the beginning...