----- Original Message ----
> From: Jorge Villalobos
> To: dev-extensions@lists.mozilla.org
> Sent: Thursday, May 29, 2008 12:30:33 AM
> Subject: Having problems with hidden browser element
> Hello,
> I'm trying to load a URL in the background, but I need the whole page to
> be loaded, specifically a Flash player inside of it. I've tried several
> approaches, such as using the hidden DOM window and having the browser
> element be 1px by 1px.
> Either of those work perfectly on Mac OS, but this is not the case on
> Windows. There seems to be some kind of restriction on what a window can
> request, depending on size and visibility. A 1x1 browser element doesn't
> work, while a 100x100 element does. I also tried the opacity CSS
> attribute, and the element works with opacity of 0.5 but not with
> opacity of 0.1.
> When I say "works", I mean I expect it to load the Flash object and
> allow it to send http requests (which it is designed to do). Does
> anybody know if there is any specific restriction on Firefox on Windows,
> or is this a problem of the Flash plugin?
> Maybe there's a better way to load the URL in the background? Notice
> that I need the Flash element to actually play, so doing a simple
> XMLHTTPRequest won't do.

What about display: none or visibility: hidden?