Hi i need some help on my menu it will not show the drop down list...

menu.css
Code:
.nav{
  list-style-type: none;
  padding: 0;
  margin: 0;
  width: 200px;
  text-transform: uppercase;
}

.nav  li{
  border-left: 10px solid blue;
  border-bottom: 1px solid red;
}

.nav li a:link,
.nav li a:visited{
  text-decoration: none;
  padding: 0.5em;
  display: block;
  background-color: yellow;
  border-left: 5px solid rgb(239,213,252);
  
}

.nav li a:hover{
  background-color: blue;
  color: #FFF;
  border-left: 5px solid green;

}

.nav ul{
  list-style: none;
  margin: 0;
  padding: 0;
  border: 0;
}

.nav ul li{
  border: 0;
  display: none;
}


.nav ul li a:link,
.nav ul li a:visited{
  background-color: orange;
  color: #FFF;
  padding: 0.5em 0.5em 0.5em 1em;
  display: block;
  text-decoration: none;
  border-left: 5px solid rgb(239,213,252);

}


.nav  li a:hover ul li {
   display: block; // I think this is my problem it will not work
}
my page


Code:
<!Doctype html>

<html lang="en">
<head>
 <meta charset="utf-8" />
 
 <link rel="stylesheet" href="menu.css" style="text/css"/>
 
</head>

 <body>
    <ul class="nav">
       <li><a href="#">T-shirt</a>
	       <ul>
		       <li><a href="#">small</a></li>
			   <li><a href="#">medium</a></li>
			   <li><a href="#">large</a></li>
	       </ul>
	   </li>
	   <li><a href="#">Brand</a></li>
	   <li><a href="#">What's new</a></li>

    </ul>	

   
 <body>



</html>