Flash Messages with Bootstrap 2 and Rails 3.2.3

application_helper.rb

module ApplicationHelper
  include FeedbackHelper

  # Your methods here

end

feedback_helper.rb

# put this in helpers directory

module FeedbackHelper

  # For flash messages
  def twitterized_type(type)
    case type
    when :alert   then "alert alert-warning"
    when :error   then "alert alert-error"
    when :notice  then "alert alert-info"
    when :success then "alert alert-success"
    else type.to_s
    end
  end

  def explain_errors(model)
    if model.present? && model.errors.any?
      html = ""
      html << content_tag(:h4) do
        <<-HERE_DOC
          #{pluralize( model.errors.count, "error")} prohibited this
          #{ model.class } from being saved:
        HERE_DOC
      end
      html << content_tag(:ul) do
        model.errors.full_messages.each {|msg|
          concat(content_tag(:li, msg, class: 'text-error'))
        }
      end
      html.html_safe
    end
  end

end

flash_messages.rb

# app/views/layouts/application.html.haml
= render "layouts/flash_messages"

# layouts/_flash_messages.haml
- flash.each do |type, message|
  %div{:class => "#{twitterized_type(type)} fade in" }
    %div{:class => 'close', 'data-dismiss' => 'alert'}
      %i.icon-remove-sign
    = message

Also check out this for more infomation. http://stackoverflow.com/a/9301461