Section 11. If a division of fence between the owners of improved land has been made either by fence viewers or under an agreement in writing between the parties which has been recorded in the office of the clerk of the town, the several occupants of such land and their heirs and assigns shall erect and maintain said fences agreeably to such division; but if a person lays his land common and determines not to improve any part adjoining the fence so divided, and gives six months' notice of his determination to all the occupants of adjoining land, he shall not be required to keep up or maintain said fence during the time that his land lies common and unimproved.