box sizing border box

html {
	box-sizing: border-box;
}

*, 
*:before, *:after {
	box-sizing: inherit;
}

html {
  box-sizing: border-box;
}
*, *:before, *:after {
  box-sizing: inherit;
}

Sintaxe formal: 
content-box | (en-US) border-box

div{
  box-sizing: border-box;
}
/* CSS box-sizing property specifies whether the padding and border of an element should be included in its total width and height or not. */