Responder helps you create responsive, mobile-first themes in Drupal. It applies CSS3 @media queries to stylesheets added by modules. This allows you to create mobile-first layouts without having to override countless module stylesheets that were designed for the desktop.

Responder does NOT alter theme stylesheets or print stylesheets, only CSS added by Drupal core and contrib modules. It is cache-aware, wrapping media queries around the preprocessed files when they are built. The media queries can be configured via the admin interface.

Example

<link type="text/css" rel="stylesheet" href="..." media="all">

Turns into

<link type="text/css" rel="stylesheet" href="..." media="all and (min-width: 720px)">