For those who haven’t heard of it, Bootstrap is a web development library that helps you get a kick-start in building the UI of your application.
It features a number of components such as buttons, button groups, dropdowns, tabs, tabbars, etc. It provides a 12-column grid for designers to base designs on, and in v2 it supports responsive design as well (support for multiple screen sized, tablet, mobile, desktop).
In addition it also includes a number of jQuery plug-ins that can make pages more interactive. These include a plugin for modal dialogs, dropdowns, scroll detection, tabs, tooltips, popovers, alert boxes, buttons; and new in Bootstrap 2 are the collapse / accordion plug-in, carousel, and typeahead. The documentation has also been improved a lot in the new 2.0 version and it is better organized, and has more examples.
Another major update to Bootstrap 2 is the way it is delivered. Now it is possible to build a custom version of the library if only selected features are needed.