Built-in Classes

pull-left class used to float element/div/module in left side. It also generates margin-right of 15px.
pull-right class used to float element/div/module in right side. It also generates margin-left of 15px.
nopadding class will remove all paddings from your element/div/module. In order to remove padding from any specific side for example left need to add nopdding-left class.
nomargin class will remove all margins from your element/div/module. In order to remove padding from any specific side for example left need to add nomargin-left class.
align-center class will include text-align center style to that element. There is also align-left & align-right class.
img-rounded class will add some border-radius into that image. img-circle & img-polaroid classes are also there to give extra bit of styles to image.