I am almost to the edge of madness looking for a tutorial about how to develop a plugin for Mac OS X lion using NPAPI but without luck. My Objective is to embed a code that i wrote in Objective-C in my page. I read mozilla docs but I dont understand how to build the proyect or even if I need to use an special template or language. Please some help.
Well, you can get a basic tutorial on NPAPI here: http://npapi.com/tutorial (there are two followup tutorials linked from there)
However, much much easier would be to just use FireBreath, which solves most of the real trouble for you; a lot of people are using it to rewrite their webkit plugins now that safari doesn't support it anymore.