The key advantage of using CSS pre-processors is nested selectors. Instead line after line of specific CSS selectors you can nest them and they will compile down for you. Check out this example:​

Bad Example: Using regular CSS, you repeat yourself a lot

Good Example: Using LESS, we can structure our CSS better

The pre-processed​ CSS then compiles to the regular CSS shown above.

We recommend using SCSS for its slightly more robust language scripting, however, the differences between LESS and SCSS are minor.

The common way to use Bootstrap's layout system is to create a basic grid which will appear as horizontal columns on the desktop but then stack on a smaller screen such as mobiles. This is done with a single set of .col-md-* classes.

Figure: Bad example - create the default stacking layout with Bootstrap

Figure:​ Bad example - the default stacking behavior on small devices

Did you know you can have more control over the responsive layout by including multiple column classes? The ability to control the layout across multiple screen sizes is a powerful tool within Bootstrap. For example, if you don't want your columns to stack on smaller devices, use the smaller grid classes by adding additional column classes (e.g. .col-xs-* .col-sm-*) to the respective <div>s.

Figure: Good example - add additional column classes to your columns

​Figure: Good example - On a smaller device, these columns now arrange horizontally as desired

Since we want our website to render corectly for all screen sizes, we specify that it should set the viewport to the size of the device's screen.

<meta name="viewport" content="width=device-width" />​

​This ensures the browser always renders at the correct resolution for the device.

By default, bootstrap will wrap the columns and make them full width on phones. If you want to hide content rather than let it wrap you can use the following classes:

• .hidden-xs
• .hidden-sm
• .hidden-md
• .hidden-lg

As well as being able to hide content per view, you can also selectively show it. This is helpful to add an extra sidebar for very large screens.

• .visible-xs
• ​.visible-sm
• .visible-md
• .visible-lg

​Bad Example: The mobile view on the right has a large unneccessary title.

Remove the title by adding the .hidden-xs class.

    <h1 class="hidden-xs">ASP.NET</h1>​

G​ood Example: The mobile view is now leaner and cleaner thanks to our .hidden-xs class.

Figure: Include respond.js in your bootstrap bundle

Note: Respond JS will be included in a new MVC5 Web Application. If you are working on an existing application, you can get it from NuGet or https://github.com/scottjehl/Respond​.

​

Figure: A new MVC5 Web Application running in IE8 with Bootstrap and Respond JS​

Figure: Bad example - using images for application icons can generate a lot of pain​

This is simplified if you are using Bootstrap, as it comes with a font-based icon library you can use in your web application. However, there is an even better third-party font-based icon library you should use when using Bootstrap: Font Awesome.

Font Awesome provides scalable vector icons that can be customized purely through CSS and some are completely free for commercial projects. This is great if you’re tight on implementation deadlines and need generic icons in a hurry. In the ideal world, a specifically custom-designed icon set is the way to go.

Using it on your project is easy, just use your email and register on their website: Get Started. Then you will be able to download and serve locally or use a CDN.

There are hundreds of icons. Here are a few commonly used ones:

​​​ ​

Figure: Examples of Font Awesome icons