The Bootstrap framework is one of the most popular libraries for developing MOBILE-FIRST, responsive web pages. Using the Bootstrap framework is the quickest way to get away from the old-school default look of web pages, and into a modern look.
Bootstrap has many navigation and widget components that give a visually pleasing design. A big advantage of knowing how to use Bootstrap is that it greatly reduces much of the CSS3 customization needed to develop a responsive web page.
Free Download for CSS3 Bootstrap Framework
Download Bootstrap for free, and take a look. It’s a very big file – 6,800 lines. There are many html tags, and ways to format them. Bootstrap does much of the heavy lifting for you.