I recently used the bootstrap video tutorial 2.0 to reference bootstrap3.0 when I was learning Bootstrap. I suddenly found many differences.

Comparison between important classes in Bootstrap 2.3 and 3.0
Bootstrap 2.x	Bootstrap 3.0
. Container-Fluid	. Container
. Row-Fluid	. Row
. Span *	. Col-MD -*
. Offset *	. Col-MD-offset -*
. Brand	. Navbar-brand
. Nav-collapse	. Navbar-collapse
. Nav-Toggle	. Navbar-Toggle
. BTN-navbar	. Navbar-BTN
. Hero-Unit	. Jumbotron
. Icon -*	. Glyphicon. glyphicon -*
. BTN	. BTN. BTN-Default
. BTN-Mini	. BTN-xs
. BTN-small	. BTN-Sm
. BTN-large	. BTN-LG
. Visible-phone	. Visible-Sm
. Visible-Tablet	. Visible-MD
. Visible-Desktop	. Visible-LG
. Hidden-phone	. Hidden-Sm
. Hidden-Tablet	. Hidden-MD
. Hidden-Desktop	. Hidden-LG
. Input-small	. Input-Sm
. Input-large	. Input-LG
. Checkbox. inline. Radio. inline	. Checkbox-inline. Radio-inline
. Input-prepend. Input-append	. Input-group
. Add-on	. Input-group-addon
. Thumbnail	. IMG-thumbnail
Ul. unstyled	. List-unstyled
Ul. inline	. List-inline

Newly Added classes in Bootstrap 3.0
Attribute	Description
Panels	. Panel. Panel-default. Panel-body. Panel-title. Panel-heading. Panel-footer. Panel-collapse
List groups	. List-group. List-group-item. List-group-item-text. List-group-item-heading
Glyphicons	. Glyphicon
Jumbotron	. Jumbotron
Tiny grid (<768 px)	. Col-xs -*
Small Grid (& gt; 768 px)	. Col-Sm -*
Medium grid (& gt; 992 px)	. Col-MD -*
Large grid (& gt; 1200 px)	. Col-LG -*
Offsets	. Col-Sm-offset-*. col-MD-offset-*. col-LG-offset -*
Push	. Col-Sm-push-*. col-MD-push-*. col-LG-push -*
Pull	. Col-Sm-pull-*. col-MD-pull-*. col-LG-pull -*
Input groups	. Input-group. Input-group-addon. Input-group-BTN
Form Controls	. Form-control. Form-group
Button group sizes	. BTN-group-Xs. BTN-group-Sm. BTN-group-LG
Navbar text	. Navbar-Text
Navbar Header	. Navbar-Header
Justified tabs/pills	. Nav-justified
Responsive Images	. IMG-responsive
Contextual table rows	. Success. Danger. Warning. Active
Contextual panels	. Panel-success. Panel-danger. Panel-warning. Panel-Info
Modal	. Modal-dialog. modal-content
Thumbnail image	. IMG-thumbnail
Well sizes	. Well-Sm. Well-LG
Alert links	. Alert-Link

Classes deleted by bootstrap 3.0
Attribute	Removed from 2.x	3.0 equivalent
Form actions	. Form-Actions	N/
Search form	. Form-Search	N/
Fluid Container	. Container-Fluid	. Container (no more fixed grid)
Fluid row	. Row-Fluid	. Row (no more fixed grid)
Navbar inner	. Navbar-inner	N/
Dropdown submenu	. Dropdown-submenu	N/
Tab alignments	. Tabs-left. Tabs-Right. Tabs-below	N/

I recently used the bootstrap video tutorial 2.0 to reference bootstrap3.0 when I was learning Bootstrap. I suddenly found many differences.