header
{
    text-align: center;
    font-weight:bold

}
h2,h3,h4{
    font-weight:bold
}
html{
    background-color: #f9f9f9(0, 0%, 66%);
padding: 25px;
font-family: 'Times New Roman', Times, serif;
}
p{font-size: 25px;}
.contenant {
    width: 70%;
    margin: 0 auto;    
    text-align: center; 
    padding: 20px;
    background-color: #f9f9f9;  
    border: 1px solid #ddd;}