Wondering what is Bootstrap?, Its a library which contains css/stylesheets, scripts, svg files, fonts etc

There are two ways to use bootstrap in Visualforce pages

  1. uploading bootstrap zip as static resources
  2. using CDN's (used in this post)

Here we go, steps for bulding a accordion page using bootstrap

STEP 1: Refer bootstrap files using CDN

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css"/>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap-theme.min.css"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js"></script>

STEP 2: Adding Accordion Body

<div class="bs-example">
    <div class="panel-group" id="accordion">
        <div class="panel panel-default">
            <div class="panel-heading">
                <h4 class="panel-title">
                    <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne">1. What is HTML?</a>
                </h4>
            </div>
            <div id="collapseOne" class="panel-collapse collapse in">
                <div class="panel-body">
                    <p>HTML stands for HyperText Markup Language. HTML is the main markup language for describing the structure of Web pages. <a href="http://www.tutorialrepublic.com/html-tutorial/" target="_blank">Learn more.</a></p>
                </div>
            </div>
        </div>
        <div class="panel panel-default">
            <div class="panel-heading">
                <h4 class="panel-title">
                    <a data-toggle="collapse" data-parent="#accordion" href="#collapseTwo">2. What is Twitter Bootstrap?</a>
                </h4>
            </div>
            <div id="collapseTwo" class="panel-collapse collapse">
                <div class="panel-body">
                    <p>Twitter Bootstrap is a powerful front-end framework for faster and easier web development. It is a collection of CSS and HTML conventions. <a href="http://www.tutorialrepublic.com/twitter-bootstrap-tutorial/" target="_blank">Learn more.</a></p>
                </div>
            </div>
        </div>
        <div class="panel panel-default">
            <div class="panel-heading">
                <h4 class="panel-title">
                    <a data-toggle="collapse" data-parent="#accordion" href="#collapseThree">3. What is CSS?</a>
                </h4>
            </div>
            <div id="collapseThree" class="panel-collapse collapse">
                <div class="panel-body">
                    <p>CSS stands for Cascading Style Sheet. CSS allows you to specify various style properties for a given HTML element such as colors, backgrounds, fonts etc. <a href="http://www.tutorialrepublic.com/css-tutorial/" target="_blank">Learn more.</a></p>
                </div>
            </div>
        </div>
    </div>
</div>

STEP 3: Visualforce Page, finally page looks like

<apex:page >
  <title>Example of Twitter Bootstrap 3 Accordion</title>
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css"/>
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap-theme.min.css"/>
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js"></script>
  <style type="text/css">
      .bs-example{
          margin: 20px;
      }
  </style>
<div class="bs-example">
    <div class="panel-group" id="accordion">
        <div class="panel panel-default">
            <div class="panel-heading">
                <h4 class="panel-title">
                    <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne">1. What is HTML?</a>
                </h4>
            </div>
            <div id="collapseOne" class="panel-collapse collapse in">
                <div class="panel-body">
                    <p>HTML stands for HyperText Markup Language. HTML is the main markup language for describing the structure of Web pages. <a href="http://www.tutorialrepublic.com/html-tutorial/" target="_blank">Learn more.</a></p>
                </div>
            </div>
        </div>
        <div class="panel panel-default">
            <div class="panel-heading">
                <h4 class="panel-title">
                    <a data-toggle="collapse" data-parent="#accordion" href="#collapseTwo">2. What is Twitter Bootstrap?</a>
                </h4>
            </div>
            <div id="collapseTwo" class="panel-collapse collapse">
                <div class="panel-body">
                    <p>Twitter Bootstrap is a powerful front-end framework for faster and easier web development. It is a collection of CSS and HTML conventions. <a href="http://www.tutorialrepublic.com/twitter-bootstrap-tutorial/" target="_blank">Learn more.</a></p>
                </div>
            </div>
        </div>
        <div class="panel panel-default">
            <div class="panel-heading">
                <h4 class="panel-title">
                    <a data-toggle="collapse" data-parent="#accordion" href="#collapseThree">3. What is CSS?</a>
                </h4>
            </div>
            <div id="collapseThree" class="panel-collapse collapse">
                <div class="panel-body">
                    <p>CSS stands for Cascading Style Sheet. CSS allows you to specify various style properties for a given HTML element such as colors, backgrounds, fonts etc. <a href="http://www.tutorialrepublic.com/css-tutorial/" target="_blank">Learn more.</a></p>
                </div>
            </div>
        </div>
    </div>
</div>
</apex:page>

Final Output