Why does auto attribute for margin not work vertically while it works horizontally?

Question

I have seen that while developing websites, vertically centering a container (of fixed height) inside a container of random height always comes as a nightmare for the web de

Answer 1

css ----------------

.aligncenter{
      display: -webkit-box;
      display: -moz-box;
      display: box;
      -webkit-box-align: center;
      -moz-box-align: center;
      flex-align: center;
      -webkit-box-pack: center;
      -moz-box-pack: center;
      flex-pack: center;
}

html -------------------------

---your content appear at the middle of the parent div----

note----------- this css class work with almost all browsers