Bootstrap de twitter could be considered a framework that combines HTML 5, CSS and Javascript.
Its mission is to simplify the process of web design especially delicate concepts as browser compatibility.
But its greatest value is the ability to responsive or fluid design.

With responsive designing we got our web adapted by device.
To be more exact the web adapts according to the device resolution or browser window size.

To summarize its main features are:
  •  Contain JQuery
  •   CSS generated using LESS system
  •  Standard CSS3 y HTML5
  •  Easy integration
  •  Compatible with multiple browsers
  •  By default have a lot of Layouts for different resolutions

We have been pioneers in using Bootstrap en Joomla! applying it on our own website with excellent results