CSS code for underline style for menu items

Question

I would like to know the CSS code used to make the underline effect for the menu items of this website : https://www.kevin-missud-charpente.fr/

Thanks in advance.

Answer 1

this is better

body,html {
  margin: 0;
  font: bold 14px/1.4 'Open Sans', arial, sans-serif;
  background: #fff;
}
ul { 
  margin: 150px auto 0; 
  padding: 0; 
  list-style: none; 
  display: table;
  width: 600px;
  text-align: center;
}
li { 
  display: table-cell; 
  position: relative; 
  padding: 15px 0;
}
a {
  color: #000;
  text-transform: uppercase;
  text-decoration: none;
  letter-spacing: 0.15em;
  
  display: inline-block;
  padding: 15px 20px;
  position: relative;
}
a:after {    
  background: none repeat scroll 0 0 transparent;
  bottom: 0;
  content: "";
  display: block;
  height: 2px;
  left: 50%;
  position: absolute;
  background: #000;
  transition: width 0.3s ease 0s, left 0.3s ease 0s;
  width: 0;
}
a:hover:after { 
  width: 100%; 
  left: 0; 
}
@media screen and (max-height: 300px) {
    ul {
        margin-top: 40px;
    }
}

<ul>
  <li><a href="#">Home</a></li>
  <li><a href="#">About</a></li>
  <li><a href="#">Contact</a></li>
  <li><a href="#">Support</a></li>
</ul>

this is on hover underline effect