HTML and CSS Reference
Bootstrap is a free, open-source collection of tools for creating responsive web sites 3 and web applications . The
templates of Bootstrap are based on HTML5 and CSS3, and cover navigation, typography, forms, buttons, and other
modern browsers, and gracefully degrades when used on older browsers such as Internet Explorer 8.
Figure 11-7. A Bootsrap template
The modular structure of Bootstrap relies on a set of LESS style sheets called bootstrap.less , making it possible
to use variables, functions, operators, nested selectors, and mixins.
The default grid system for Responsive Web Design comes with a 1,170 pixels wide grid layout, however, web
designers can choose a variable-width layout as well. The four target device classes in both cases are mobile phones
with portrait and landscape orientation, tablets and desktop computers with low and high resolution screen. Selecting
a device class modifies the width of the columns.
To use Bootstrap in the markup, you have to download the CSS file of Bootstrap and link it in the document head.
Alternatively, the CSS file from the downloaded Less or Sass style sheets can be compiled with a special compiler. If
3 Since version 2.