Answers for "change size of border css"

border width css

.element {
  border-width: 2px;
}

border width css

element {
	border-width: 10px;
  	/* Or use shorthand border property */
  	/* width style colour */
  	border: 10px solid black;
}

how to style rule to apply the Border Box model css

header, ul, nav, li, a /* other elements */{

 display: block;
   -webkit-box-sizing: border-box;
   -moz-box-sizing: border-box;
   box-sizing: border-box;