Multi-resolution (HTML5 or not) games.

How to conform your game content to the available screen space ?
How to appropriately handle retina display resources ?
How to deal with the million different screen resolutions available and have your game gracefully up/down scale ?

This post describes how this problem is Addressed in Cocos2d-html5 V4, the API available for this purpose and how to handle special cases like orientation change requests.