使用.btn-danger类可以为按钮设置危险动作，即元素的红色背景色。
您可以尝试运行以下代码来实施危险动作-
<!DOCTYPE html> <html> <head> <title>Bootstrap Example</title> <link href = "/bootstrap/css/bootstrap.min.css" rel = "stylesheet"> <script src = "/scripts/jquery.min.js"></script> <script src = "/bootstrap/js/bootstrap.min.js"></script> </head> <body> <div class = "container"> <button type = "button" class = "btn btn-primary btn-block">Categories</button> </div> <div class = "container"> <a href = "#">Tech <span class="badge">95</span></a><br> <a href = "#">Entertainment <span class="badge">30</span></a><br> <a href = "#">Research <span class="badge">9</span></a><br> <a href = "#">Viral <span class="badge">20</span></a><br> <a href = "#">Sport <span class="badge">105</span></a> </div> <div class = "container"> <br><p>Do not click below:</p> <button type = "button" class = "btn btn-danger">Danger</button> </div> </body> </html>