They have done the hard work for you. They have done the CSS and Java Script and useful components. It contain useful templates (Marketing site, Fluid Layout and etc) so you don't have to waste time fixing the layouts and making them compatible with all the web browsers. You can even build responsive website for any computer device.You only need to download the 83 Kb file, unzip it copy it to main web directory and start building the website.
This is simply awesome. If you experienced with HTML CSS and JavaScript you just have to get used to its CSS selectors JavaScript classes. That can be achieved in couple of hours. They have a really good documentation that will help you to learn Bootstrap easily.
No need to talk more everything can be found here and I am sure it is going to make your web developing life much easier and smooth.
