html {  
       background: url(2013.jpg) no-repeat center center fixed; 
       -webkit-background-size: cover;
       -moz-background-size: cover;
       -o-background-size: cover;
       background-size: cover;
       }

#x {
margin: 25% 25%;
padding: 5px;
font-family:  Arial, sans-serif;
font-size: 30px;
color: #111;
opacity: .85;
background: #ccc; 
text-align: center; 
}
#z { 
font-size: 16px;

 }

a {
color: #333;
}