Media Query

Media queries consist of a media type along with one or more expressions that conditionally check for certain media features, particularly that of screen sizes. The logical expressions in a media query can be either true or false; it is true if the media type of the query matches that of the media type of the device where the user agent (Web browser) is running on; otherwise, it is false. When the media query results to true, then the corresponding style rules specified will be applied, following normal cascading rules. It must be noted that, even if the query results to false, style sheets specified within the <link> tag are still downloaded, but are simply not applied.

Example using the HTML <link> tag:

<link rel="stylesheet" media="(max-width: 600px)" href="specific.css" />

Example using @media within the <style> tag:

<style>
@media (max-width: 500px){
.left_sidebar {display: none; }
}
</style>