html,body{
    margin: 0;
    padding: 0;
}
a{
    text-decoration: none;
}
header{
    width: 100%;
}
header img{
    width: 50%;margin:40px auto 40px;
    display: block;
}
main{
    width: 100%;
}
.first,.second,.third,.fourth{
    width: 100%;
    display: flex;
}
.first div,.second div,.third div,.fourth div{
    flex: 1;
}
main img{
    width: 100%;
}
footer{
    width: 100%;    
}
footer p{
    width: 80%;
    color: black;
    font-weight: 700;
    margin: 40px auto 40px;
    text-align: center;
}
@media screen and (min-width: 1000px){
    html,body{
        width: 1000px;
        margin: 0 auto;
    }
}