Vanilla Bootstrap’s components/widgets require their parts of the DOM to conform to certain structures. Apple Developer Program Membership Required The Download on the App Store badge and the Apple product images shown in these guidelines are for use only by Apple Developer Program members who have agreed to the App Marketing Artwork License Agreement. Add custom media queries to change the grid size breakpoints for print media only. Validators In order to provide the best possible experience to old and buggy browsers, Bootstrap uses CSS browser hacks in several places to target special CSS to certain browser versions in order to work around bugs in the browsers themselves. The information in these guidelines is subject to change.