为什么我的页面没有效果呢 粘贴别人的代码也没有效果
<!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>菜单标题</title> <link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css"> <link rel="stylesheet" href="style.css"> </head> <body> <div class="dropdown"> <button class="btn btn-default dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown"> 下拉菜单 <span class="caret"></span> </button> <ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1"> <li role="presentation" class="dropdown-header">第一部分菜单头部</li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li> <li role="presentation" class="divider"></li> <li role="presentation" class="dropdown-header">第二部分菜单头部</li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li> </ul> </div> <div class="dropdown"> <button class="btn btn-default dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown"> 食物 <span class="caret"></span> </button> <ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1"> <li role="presentation" class="dropdown-header">水果</li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">苹果</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">香蕉</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">梨</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">桃</a></li> <li role="presentation" class="divider"></li> <li role="presentation" class="dropdown-header">蔬菜</li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">芹菜</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">萝卜</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">茄子</a></li> <li role="presentation" class="divider"></li> <li role="presentation" class="dropdown-header">主食</li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">米饭</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">馒头</a></li> <li role="presentation"><a role="menuitem" tabindex="-1" href="#">面条</a></li> </ul> </div> <script src="http://libs.baidu.com/jquery/1.9.0/jquery.js"></script> <script src="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script> </body> </html>
点击按钮没有效果 为什么呢 是我的原因吗
