combining media queries css code example

Example 1: how to combine two screen sizes in media queries css

@media (min-width: 30em) and (max-width: 50em) { ... }

Example 2: media query in html style

span { background-image: url(particular_ad.png); }

@media (max-width: 300px) {
    span { background-image: url(particular_ad_small.png); }
}