Learn how to easily customize bootstrap forms. Using Twitter Bootstrap's center-block helper class, which is available in Bootstrap 3.2, you may center a div.. center-block class contains following css code.center-block { display: block; margin-right: auto; margin-left: auto; } Objective. Using them alongside valuable content might bring a lot of business value to your project. Modal Form Bootstrap Modal Form. Bootstrap - Forms - In this chapter, we will study how to create forms with ease using Bootstrap. Example