Twitter Bootstrap is a CSS framework developed to make designing your web pages easier. It provides the default nice-looking style for typography, tables, forms, buttons, images and so on, so you can create a professionally looking page in a minute.
The grid system provided by the Bootstrap allows to arrange elements on your web page in a grid with rows and columns. The grid adapts to different screen resolutions, making your page equally well-readable on mobile phones, tablets, desktops and wide screens.
Bootstrap is shipped with Zend Skeleton Application, so you can start using it out of the box or, alternatively, you can download the newest version of Bootstrap from the project's page and customize it as you wish.