size large add this class .btn-lg
active state add this class .active
disabled state add this disabled="disabled"
dropup variation trigger dropdown menus above elements by adding .dropup to the parent.
block level buttons add this class .btn-block
button toolbar combine sets of
nesting place a .btn-group within another .btn-group when you want dropdown menus mixed with a series of buttons.
small
large
extra large
size small add this class .btn-sm
size extra small add this class .btn-xs
split button dropdowns similarly, create split button dropdowns with the same markup changes, only with a separate button.
buttons group wrap a series of buttons with .btn in .btn-group
