Shavua Tov. We Israelis read Parshat Acharei-Mot today and we will be on a different schedule from our Diaspora counterparts. They celebrated יום טוב שני and will read אחרי מות next week.
One of the lesser known subjects alluded to in the Parsha, is היתר במות. This refers to a brief period in our history when there was in between time when there was no Mishkan or Beit Hamikdash.
People were allowed to make their own altars during this time and offer sacrifices. They were only allowed to offer free will offerings but not obligatory sacrifices. Once the Mishkan or Beit Hamikdash stood, it was forbidden to offer any sacrifices anywhere else. Non-Jews were also allowed to offer free will sacrifices as well in the Mishkan or Beit Hamikdash.
This temporary period of so called home-made altars was the period known as היתר במות.