I intend to build a HttpModule in order to scan a response's source and make small adjustments, mainly altering urls (hrefs, actions, srcs, etc).
I see the HttpApplication has a plethora of events that can be handled and I'm not sure of the best stage at which it's safe to alter the HTML content that goes back to the browser.
I need to do this in a HttpModule because this is an application-wide processing that spares me of writing the same code in every page.
You could use a response filter that you could attach during
BeginRequest. And here's a nice video.