How to visualize HTML/XML files in Emacs?

[Marcin Borkowski]

Hello there,

so I have this HTML (or XML) file, and it is a mess as far as indenting
and newline characters go.  I'd like to either pretty-print it, or maybe
convert to s-expressions, or visualize it in any other way.  What would
you recommend?  I know (from this answer on ESE:
http://stackoverflow.com/a/6247579) about sgml-pretty-print, and it
works nice.  Any other suggestions?

Bonus points if it could be done with skewer-mode (or something), so
that the HTML is taken from the browser.  (Notice that even if I'm
browsing a local file, which I am, just grabbing the file won't help,
since I modify the DOM in the browser with JavaScript.)

TIA,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University