Embed a web browser into a page

[Carbon Man]

Hi,
I need to embed a web browser into a python page. I am coming from the MS 
world where I created an app that all of it's interfaces were actually web 
pages rendered in an Internet Explorer activex control. There was a object 
hook that allowed you to call into the host environment from javascript. 
Basically the host environment would receive the documentComplete event and 
call a method in the document's Javascript passing in an object reference. 
That reference would then be available for calls to be made from Javascript 
back into the host environment.
I am just starting to explore the Pythonic programming jungle and I was 
wondering if there is a way to do something similar that would work 
cross-platform?
I guess there is much more complexity in it when you start to go across o/s 
platform boundaries. The common web interface would then be Gecko or WebKit?
So can someone suggest what would be required to build a cross-platform 
Python app that was capable of browsing HTML files, receiving events from 
the browser, and that allows the embedded page to call host Python modules 
from Javascript via an object reference? Or I am asking too much :)