header{
    margin: 20px auto;
    width: 910px;
    height: 100px;
}
header .logo{
    width: 100px;
    height: 100px;
    background-color: navy;
    float: left;
    margin-right: 10px;
    border: 3px solid black;
    box-sizing: border-box;
}
header .banner{
    width: 800px;
    height: 100px;
    background-color: navy;
    float: left;
    border: 3px solid black;
    box-sizing: border-box;
}
nav{
    margin: 20px auto;
    width: 740px;
    height: 40px;
    /* background-color: red; */
    /* kc   ku */
}
nav li{
    margin-right: 10px;
    width: 140px;
    height: 40px;
    background-color: navy;
    list-style-type: none;
    float: left;
    text-align: center;
    line-height: 36px;
}
nav li:last-child{
margin-right: -10px;
}
nav li a{
    text-decoration: none;
    color: white;
    font-size: 16px;
    font-weight: bold;
    font-family: Arial, Helvetica, sans-serif;
    letter-spacing: 1px;
    border: 2px solid black;
    box-sizing: border-box;
    display: block;
}
nav li a:hover{
    color: navy;
    letter-spacing: 3px;
    background-color: white;
    border: 2px dashed black;
}