Completed 406 Not Acceptable in 26.0ms while trying to respond json

i am trying to create an app with angular and rails.as a first step i am
trying my controller to give json response , in which i am failing with
the below error

Completed 406 Not Acceptable in 26.0ms

my controller-------

class TodosController < ApplicationController
  respond_to :json

  def index
    #respond_with :@todo
    @todo=Todo.all
    respond_to do |format|
      format.json { render :json => @todo}

  end
  end
  end

routes.rb------

resources :todos

gemfile--------

source 'https://rubygems.org'

gem 'rails', '3.2.17'
gem 'pry-nav'

# Bundle edge Rails instead:
# gem 'rails', :git => 'git://github.com/rails/rails.git'

gem 'activerecord-jdbcsqlite3-adapter'
gem 'jruby-openssl'

group :development, :test do
  gem 'ffaker'
  gem 'factory_girl_rails'
  gem 'rspec-rails'
  gem 'shoulda'
  gem 'shoulda-matchers'
end

# Gems used only for assets and not required
# in production environments by default.
group :assets do
  gem 'sass-rails', '~> 3.2.3'
  gem 'coffee-rails', '~> 3.2.1'

  # See https://github.com/sstephenson/execjs#readme for more supported
runtimes
  gem 'therubyrhino'

  gem 'uglifier', '>= 1.0.3'
end

gem 'jquery-rails'

Copy/paste here the section of development.log leading to the error.

Colin