As per Bootstrap official website, "Bootstrap is the most popular HTML, CSS, and JS framework for developing responsive, mobile first projects on the web."
Bootstrap has been designed to focus on responsive design where a website can adapt its design based on screen from which it is being browsed. With the advent of mobile, tablets and other small devices responsive design was the need of an hour.
Look at below pictures when this website "TechFunda.com" screen shot has been taken both in Desktop and Mobile.
Above is TechFunda.com design layout when it is browsed from bigger screens like laptop or desktop. If the same website is browsed from mobile device, the layout changes automatically and it looks like below.
Notice main menu bar and left panel side bar of the desktop design. Both has changed from bar to a dropdown menu (highlighted).
All this happened because of use of css classes written as part of Bootstrap (a css framework).Views: 3161 | Post Order: 2