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Bootstrap-3 Interview Questions
Bootstrap is a powerful front-end framework for faster and easier web development. Bootstrap is the most popular HTML, CSS and JavaScript framework for developing responsive, mobile-first web sites.
Inside the container, the .row class is used to contain the grid columns. Rows should always be placed inside of a container (.container or .container-fluid) to ensure 

proper spacing (between page content and the edge of the browser). 

The Bootstrap .row uses negative margins (-15px) to counteract the padding (15px) of the container. The end result is no visual spacing (margin or padding) on the 

sides of the row within the container. There are several reasons why the “negative margin” approach is used in Bootstrap.
The key components of Bootstrap are:

CSS : It comes with plenty of CSS files
Layout Components : List of layout components
JavaScript Plugins : It contains many jQuery and JavaScript plugins
Scaffolding : It gives a basic structure with link styles, Grid system and background
Customize : To get your own version of framework you can modify your components.
All grid systems have spacing or “gutters” around columns. In the case of Bootstrap, the gutter is created using padding of 15px around each column. The effective 

gutter displayed between neighboring columns in 30px. The outer columns (leftmost & rightmost) need to have 1/2 of the gutter (15px) on the outside to keep spacing 


The relationship between .container and .row is made complete with columns (col-*). Each row is divided horizontally using Bootstrap’s column classes col-*.
Bootstrap has a 12-unit grid (instead of 10, 16, etc..) is that 12 evenly divides into 6 (halves), 4 (quarters) and 3 (thirds). This makes adapting to a variety of 

layouts much easier. Bootstrap’s grid columns are identified by different col-(breakpoint)-(units) CSS classes. So for example, col-md-3 would be a column that takes up 3 of the 12 units (or 25%) across in a row.

These grid sizes enable you to change the layout of columns to best match different screen widths and devices__ the essence of responsive design.

xs  :  for the smallest screen widths like smartphones < 768 px
sm  : for small screen widths like smartphones and tablets >= 768 px
md  : â€Šfor medium screen widths like tablets and laptops >= 992 px
lg  :  for large screen widths like desktops >= 1200 px.
Bootstrap 3 supports all the modern browsers with latest version i.e. Firefox, Google Chrome, IE (Internet Explorer), Opera and Safari.
Tables can be easily made with basic html tag and specific classes provided in Bootstrap 3. You can make table with Striped rows, bordered table, hover rows, condensed 

table and responsive table using their specific classes for right results. Read more about Bootstrap 3 tables here.
Yes we can make images responsive by adding class .img-responsive which in turn applies CSS properties with max-width(100%)  as well as height (auto) for covering parent element.
Offset columns are used for more specialized layouts. For more spacing they can be used by pushing column over.

For example :  .col-xs=* classes do not support offset but they are easily simulated using an empty cell.