Progressive Enhancement.

Progressive enhancement is a strategy for web design that emphasizes accessibility, semantic HTML markup, and external stylesheet and scripting technologies.

Progressive enhancementWikipediaJuly 20th, 2019
The Role of Enhancement in Web DesignNielsen Norman GroupMay 1st, 2016
Progressive Enhancement: Past, Present, and FutureTreehouseNovember 17th, 2014
Progressive Enhancement and the Content-out ApproachUIENovember 20th, 2013
Understanding Progressive EnhancementA List ApartOctober 7th, 2008