Thanks for your reply.
I do believe that
according to this, Firebug is
supposed to be able to do what I'm searching for.
However, in the real world, it doesn't quite work as well, because while it will show what took how long after the page (or the respective page element) has finished loading, it does not reliably show what it's stuck at
while it's still loading.
This image shows archive.org having problems (archive.org isn't the most reliable of websites, in my experience). The page is still loading, but Firebug doesn't show what specific element/file is stalling things:
The second below screenshot shows the same page a minute or so later, after archive.org has finished loading. (The page hasn't actually loaded successfully, but that's archive.org's problem, not Firebug's. Firebug is supposed to be able to help pinpointing the problem.) It now turns out that index.php was at fault -- mind you, index.php showed as (instantly) fully loaded in the earlier screenshot:
So... does anyone know another solution that works better? Or a way to make Firebug work as intended?
PS: In case you're wondering, I get the same results with AdBlock Plus turned off, maybe a bit quicker, but that's all.