Some tips in CSS

hiddenPorperty.css

.element {
  /*apply: display: inline-block;*/
  float: left;
}
.element {
  /*apply: width: inherit; height: inherit;*/
  display: inline;
}
.element {
  /*apply: height: 100px; vertical-align: middle;*/
  line-height: 100px; 
}
.element1, .element2 {
  /*apply: float: left; top: 0;*/
  display: inline-block;
  vertical-align: top;
}

/*Select and style every <p> element that is the first child of its parent:*/
p:first-child { 
    background-color: yellow;
}