rails的字符编码

想练练手，随意的写了个登陆页面，简单的只有几行。

<%= form_tag('login_check') do -%><%= text_field_tag 'user_name', 'Enter your search query here' %><br><%= password_field_tag 'user_password' %><br><%= submit_tag '登录' %><%= button_tag '清空' %><% end -%>

却发现，报错了，页面显示

We're sorry, but something went wrong.

If you are the application owner check the logs for more information.

在日志中查看到：

ActionView::Template::Error (Your template was not saved as valid UTF-8. Please either specify UTF-8 as the encoding for your template in your text editor, or mark the template with its encoding by inserting the following as the first line of the template:

# encoding: <name of correct encoding>.

了解到是因为字符编码的问题