html{
    font-size: 19px;
}
nav{
    font-size: 16px;
}
footer{
    font-size: 16px;
}
a{
    border-left: 2px solid rgba(108, 117, 125, 0.5)
}

@media (max-width: 767px) { 
    div { 
      /* default is 1rem or 16px */ 
      font-size: 20px; 
    }
    a {
        border-left: none;
    }
  }
.cena {
    height: 40px;
    text-align: center;
    background-color:yellowgreen
}

#main-button{
    margin-top: -30%;
    position: relative;
    left: 50%;
    -webkit-transform: translate(-50%, -50%);
    -moz-transform:translate(-50%, -50%);
    -o-transform:translate(-50%,-50%);
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -60%);
}