Now with this title I am not saying that you should throw away JQuery etc… not at all… Lord knows I never will. But Mozilla has created a lighter version of JQuery to assist with Mozilla OS development and mobile HTML5 app development in general. When you download Mortar to have a play you will notice it is included.
I am playing with Mortar and it is a great kit to get your started with HTML5 mobile apps. Does it mean I will go to replacing JQuery with Zepto… probably not but for paying around with some Mozilla prototypes it seems quite nice. Though you have to ask yourself do I want to learn yet another Javascript library… Though that is the thing about web development and now it seems mobile development I think the acronym could be “YAJSTL” Yet Another Java Script Library to Learn 😉
Zepto Home Page http://zeptojs.com/
Writing Web Apps with Mortar https://hacks.mozilla.org/2013/01/writing-web-apps-quickly-with-mortar/