html{
    background-image: url('grey.png');
    background-repeat: no-repeat;
    background-position:center;
    background-attachment: fixed;
    background-size:100% 100%;
    font-family:arial;
    font-size:20px;
    color:black;
}

header h1{
    text-align:center;
    color:navy;
}

nav ul li{    
    list-style-type:none;
    display: inline;
    margin-left:20%;
}
nav ul li a:link{
    color:black;
}
nav ul li a:visited{
    color:purple;
}
nav ul li a:hover{
    color:red;
}
nav ul li a:active{
    color:green;
}

#number{
    display:block;
    margin-left:auto;
    margin-right:auto;
    margin-top: 100px;
    text-align:center;
}
.content{
    text-align:center;
}
.content img{
    width: 300px;
    height:200px;
    padding: 25px;
    border-radius:50px;
}
footer{
    text-align:center;
}