@media only screen and (min-width: 1000px) {
    header {
       z-index: 1;
	   position: absolute;
	   top: 0px;
	   width: 100%;
    }
}

@media only screen and (max-width: 500px) {
    .nav li {
        margin-left: 2px !important;
        margin-right: 2px !important;
        width: 20vw;
    }
}
@media only screen and (min-width: 501px) and (max-width: 999px) {
    .nav li {
        margin-left: 2px !important;
        margin-right: 2px !important;
        width: 100px;
    }
}