*{
    /*bloco de reset*/
    box-sizing: border-box;
}
body{
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    background-color: #f4f4f4; /*cor em hexadecimal*/
}
header{
    background-color: #c0c0c0;
    color: #ffff; /* branco em hexadecimal*/
    text-align: center; /*centraliza o texto*/

}
nav a{ /*nav navgation a a, de link , vou trabalhar so no link*/
    color: blue;
    text-decoration: none; /*tirei toda a decoraçao do texto*/
    padding: 4px;
}
.bloco{ /*declaraçao da class, a class procede de "." */
    background-color: #cccc;
    color: black;
    border: 1px dotted #a3a3;
    border-radius: 6px;
    padding: 16px;
    margin-bottom: 16px;
    border-top: 2px solid ;


}