How To Specify Css For Smaller Screen

@media only screen and (max-width: 991px) and (min-width: 769px){
/* CSS that should be displayed if width is equal to or less than 991px and larger
than 768px goes here */
}

@media only screen and (max-width: 991px){
/* CSS that should be displayed if width is equal to or less than 991px goes here */
}

@media screen and (min-width: 1400px) {
.container {
width: 1370px;
}
}
@media screen and (min-width: 1600px) {
.container {
width: 1570px;
}
}
@media screen and (min-width: 1900px) {
.container {
width: 1870px;
}
}