enable overflow-y scroll

  
    div.ex1 {
  overflow-y: scroll;
}

div.ex2 {
  overflow-y: hidden;
}

div.ex3 {
  overflow-y: 
    auto;
}

div.ex4 {
  overflow-y: visible;
}
  
 

    div.ex1 {
  overflow-y: scroll;
}

div.ex2 {
  overflow-y: hidden;
}

div.ex3 {
  overflow-y: 
    auto;
}

div.ex4 {
  overflow-y: visible;
}