There are 4 links tagged.
http://sixrevisions.com/css/responsive-background-image/
Added: 01/07/14 Tags: responsive CSS background
http://alistapart.com/article/can-email-be-responsive
Added: 20/05/14 Tags: responsive HTMLemails
http://stuffandnonsense.co.uk/projects/320andup/
Added: 25/01/12 Tags: responsive
Added: 26/07/11 Tags: responsive