CSS for mashup responsiveness

Hi,

Is it possible to define the mashup resolution to a desired resolution (eg:1366*768) using css?

@media all and (max-width: 1366x) and (min-height: 768px) {
 body {
 background: #ccc;
 }
 .someclass {
 padding: 10px;
 }
}

Can I implement the script directly in my custom css space? Please provide some idea.

Thanks,

Shalini V.