in reply to How to replace the output (new html page)?
You are searching for some kind of server push with HTTP. It can be done -- look at a Bugzilla's after-search "munching bugs" screen.
I'm not familiar with it, but I suspect it is a case of sending two files with "Content-Disposition: inline" and some sort of MIME splitting to distinguish the two HTML pages. Try to find out more by reading the Bugzilla source.
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