Bootstrap DropDown没有加载

Question

使用以下W3Schools的示例：W3Schools DropDown

我跟着这个例子，但它不适合我。这就是我想要的地方：

Follow these steps 
1 ==> ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"

2 ==> sudo rm -rf /usr/local/Homebrew/
      sudo rm -rf /usr/bin/Homebrew/

3 ==> install brew
      1 -- /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

      2 -- sudo chown -R $(whoami) /usr/local/var/homebrew

If get these error try below command
  Error: Failed to link all completions, docs and manpages:
        sudo chown -R $(whoami) /usr/local/*

  then follow these commands
        /usr/local/bin/brew update --force

老实说，我不明白为什么这不起作用。我的css文件包含正确的代码。