Not every Anglican diocese worldwide has a Web page yet. The web page that you are now reading is operated by the Society of Archbishop Justus as a placeholder until The Diocese of Niassa is prepared to have its own page. The Society operates the domain ANGLICAN.ORG in trust for the Anglican Communion; niassa.anglican.org, a subdomain issued to the Diocese of Niassa, is part of what is being held in trust.
If you represent the staff of The Diocese of Niassa and would like to learn how to take ownership of the name niassa.anglican.org please see http://anglican.org/domain/ and read about the naming plan.
If you are looking for an official home page for The Diocese of Niassa we do not know of one. Should you find it before we do, please do let us know about it. Sometimes Anglicans Online lists unofficial diocesan pages.