It's not that simple. No theme seems to define CSS for the iframe border. Nothing shows up in Firebug.

Dispy got rid of the border, but even when I looked at the commit where it was removed, I still couldn't see what he did.

I should ask @Simon L'nu

@Andreas Bauer japp, kenn und hab ich, aber wie Thomas ja beschrieben hat, hilft das nicht weiter.

I can't find the iframe/border you see (visually), however the css syntax should be

iframe {
border: none;
}

You fixed it a month ago, I even thought it was impressive enough to screenshot and post elsewhere: https://kakste.com/display/bouldrake/415975

If memory serves, it was here that it changed: https://github.com/friendica/friendica/commit/20ea1b7d4bbfcfc0139b66278be383b0378b545f#view/theme/dispy/dark

But if you don't know what we're talking about, it must have been a side effect of something else.

(Edit - for clarity, Manu posted while I was typing; "you" means Simon)

And a second edit - Manu is right. Just add that line to the CSS file (assuming you kept it). And while you're there, the existing CSS file is only needed for the zeros, and only if your iframe is above about 1000px

pfff.... that was simple & easy, thanks guys and @Emmanuel Revah
It's fixed and done, just added the syntax into the plugin css file

@Oliver no problem. :]