_messages.html.erb

<%= display_messages %>

# returns {:error=>"Email/senha incorretos."}

application_helper.rb

  def display_messages
    flash.each do |name, message|
      if message.is_a?(String)
        case name
          when :error
            text = "#b94a48"
          when :warning
            text = "#c09853"
          when :success
            text = "#468847"
          when :info
            text = "#3a87ad"
          else
            text = "white"
        end
        html = <<-HTML
        <div class="alert alert-error alert-block">
          <i class="icon-remove icon-large"></i>
          #{message}
        </div>
        HTML
        html.html_safe
      end
    end
  end

# returns "        <div class=\"alert alert-error alert-block\">\n          <i class=\"icon-remove icon-large\"></i>\n          Email/senha incorretos.\n        </div>\n"