How to view Firefox functions running in a console?

I'm currently learning to become a proper developer for Firefox extensions. I have two questions here:

1. How to view Firefox's XML request?

2. From Firefox, how can I dump/trace e开发者_运维问答very functions running in a Firefox extension?

Because I would like to know, which functions are being called, and would like to see my error messages..

Thanks.

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1. LiveHTTPHeaders.
2. Venkman