def captcha_valid?(code)
      return false if session[:captcha].blank? or code.blank?
      session[:captcha].to_s.upcase == code.to_s.upcase
    end
def captcha_valid?(code)
      return false if session[:captcha].blank? or code.blank?
      session[:captcha].to_s.upcase == code.to_s.upcase
    end
validate given captcha code and re