Comment lines in ruby rails html.erb files, as answered on StackOverflow http://stackoverflow.com/a/3901665/123781

ruby-rails-erb-comments.erb

To comment a single line use

  <%-# commented line -%>

This also works

  <%# my comment %>

To comment a whole block use a if false to surrond your code like this

  <% if false %>
    code to comment
  <% end %>