css border shadow bottom only code example

Example 1: box shadow bottom only

box-shadow: 0 4px 2px -2px gray;

Example 2: box shadow to make border bottom

-webkit-box-shadow: -2px -1px 15px 7px rgba(0,0,0,0.5);
  -moz-box-shadow: -3px -2px 30px 14px rgba(0,0,0,0.425);
  box-shadow: -4px -3px 45px 21px rgba(0,0,0,0.35);