Bootstrap 3.0 div structure
here 4 class is used for set width in 4 screen size. ie. Large Desktop -----> col-lg-12 Laptop / Desktop -----> col-md-12 Ipad size -------> col-sm-12 Mobile Size ------> col-xs-12 Example:- <div class="col-lg-12 col-md-12 col-sm-12 col-xs-12"></div>