# File webapp.rb, line 234
  def check_last_modified(last_modified)
    if ims = @request_header['If-Modified-Since'] and
       ((ims = Time.httpdate(ims)) rescue nil) and
       last_modified <= ims
      @response.status_line = '304 Not Modified'
      return
    end
    @response_header.set 'Last-Modified', last_modified.httpdate
    yield
  end