www programming

but at moment there is no iframe at url you indicated
???

ok i see now, it's 1 px, but look, that you have error on code, then following js fail. Open page forum and: remove the i that prepend // or remove the line

my apologies, you take time to try to help me and I make silly errors !
However, it's corrected and if you go back to the same page http://dev.my80isfantastic.eu/phpbb_forum, still we are not able to see the iframe whereas it should be. (width is 1px and height is 0px) however, if I change it manually in js console, I can make the iframe content appear

np, look that happen every second i do messes all around. the point is finally resolve, may faster as possible.

Look that no error at moment so you want say me (check/try please)
that if you change this into page forum into something like this all will work?
what browser you're using?
well no, stupid question, since you say you're more than one to test out, i assume not all have the same browser ... by the way in any case let know, you're near to fix

p.s where you see that the iframe result with 0px height? no time at moment, i will be over on afternoon ... return back soon

just starting something else, just before a fast look here to help you finally resolve ...
ok, i see ...
so ... original page forum contain this style for iframe element: in effect, this is it also into page source code, your html output is this: BUT, like you said, if i look into console, the output is as you say this: it result added of height: 0px; ...
so asking to myself, that at moment unique plausible explain, what javascript you have, of which activated plugin in wp, or js template function, that cause to modify the attribute style of the iframe element on page, despite it is with an id?
The (in case) wrong concept of the js function that cause this, should aim to precise iframe, and not any existent iframe on page, so causing this ... what you think?

Provide here in reply, if you want:
the page forum you're using, and the page template of your wp theme

may element's you wrap the iframe into, are causing this. Removing should resolve