box sizing and opacity code example

Example 1: css opacity

.div{
  opacity: 0.8; /* 1 means fully visible, 0 means invisible */
}

Example 2: 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;