CSS media query for exact viewport width

Yes, in CSS it is possible to use @media rules to target an exact width.

CSS Example

@media (width: 980px) {
  /* Your CSS */
}

This is telling the browser, when the viewport width is exactly 980px wide, apply the following CSS. When your viewport width changes to 981px or 979px or anything that isn't 980px wide, the CSS will be removed.

Unlike the other answers, this is not using max-width or min-width because the @media rules allow you to just define width, which will target the exact measurement you give it. The width is defined using the viewport width.

Note: You can learn more about the CSS3 @media rule from W3 Schools. Specifically if you look under Media Features, you'll see the available variables, including width all the way at the bottom.

You could do something like this. The media query will be triggered at 980px width and would work for width no greater than 980px.

 @media screen and (min-width: 980px) and (max-width: 980px) {
     html {background-color: red !important;}
 }

 html {background-color: green; min-height: 300px;}