Use only relative sizes (rem, em, %, etc.) for media query breakpoints
To define media query breakpoints, it is advisable to use relative units only (such as rem, em ou %) for the CSS @media rule.
@media (max-width: 25rem) {
nav li.tile {
width: 33%;
}
}
Rather than absolute units such as px, pt, cm, etc.
Note
This recommendation also applies for media queries directly integrated in the <link /> tag:
<link rel="stylesheet" href="/css/extra-small.css" media="all and (max-width: 25rem)" />