# GET /twits
  # GET /twits.xml
  def index
    if params[:target_user]
        target_user = User.find_by_name(params[:target_user])
        @twits = Twit.find(:all, :conditions => [ "user_id = ?", target_user.id ], :order => 'created_at desc')
    else
        @twits = Twit.find(:all, :conditions => [ "user_id IN (?)", current_user.following_user_ids.push(current_user.id) ], :order => 'created_at desc')
    end
    @twit = Twit.new

....