It totally depends on your accent! In Canada, we say era "air ah" and error "air or".

I'm not a native speaker, but I show you the easiest trick to know the differents, http://translate.google.com/#auto|en|error click "listen" the one that have a "speaker" icon in it, so you able listen to how it pronounce error. http://translate.google.com/#auto|en|era click "listen" the one that have a "speaker" icon in it, so you able listen to how it pronounce era. You also can install encarta dictionary, it provide you with pronounce tools that can show you how the each words is pronounce in English. Hope this will help you.

There are pronounciations of the two here: http://en.wiktionary.org/wiki/File:En-us-era.ogg http://en.wiktionary.org/wiki/File:en-us-error.ogg It seems you understand phonetics so you should be able to go back and discern the difference.

era= "ee-raah" error="eh-ruhrr"

I am not native speaker, but let me try to answer... era ---- yi ra (in chinese pronounciation) error --- eh (like in echo) and reur (like in her)....