I thought it might be because I was moving to mouse pointer to the slide bar on the right but even intentionally holding it still this still happens.
Check the settings here;
Firefox (Options / Tools) > Tabs.
Do you see a visible switch, in other words, the new window comes up but promptly moves behind the window from which it was opened? That can be caused by a bug in the Flash player plugin's protected mode feature. More information and workarounds in this thread: Opening New Windows and Shockwave Flash.
I'm not sure about that. I will be more attentive and make a note if that does happen.
Open new windows in a new tab instead X Warn me when closing multiple tabs X Warn me when opening multiple tabs might slow FF
Don't load tabs 'til selected When I open a link in a new tab... Show tab previews in the windows taskbar
These are the current settings under Options/Tabs (X=checked)
Here's what happens: I opened, in a new window, an article on a forum. Within that window I clicked a link. The forum has a setting whereby links are automatically opened in new windows. The new window did open and had focus momentarily - it then moved back and the 'parent' window regained focus. I closed both the parent and newly opened windows and returned to the forum main page. I immediately reopened the article and clicked the link within. This time the new window opened and retained focus - as one would expect.
I then shut down FF and repeated this process and got the same results.
So, is the flash player issue mentioned?
Hi fforie, to diagnose this as the Flash protected mode issue, keep one window open with some Flash loaded in it. I think the YouTube home page loads Flash without starting anything playing. If that solves the problem in the forum scenario, then yes, I think Protected Mode most likely is the issue.
re: starting youtube first (to get flash running)
jscher2000, it looks like that's the ticket! Thanks for the info!
As an aside, I experimented by first starting youtube in internet explorer and this had no effect on the window behavior.
Hi fforie, on the IE point, that makes sense. Adobe publishes different Flash players for IE (ActiveX technology) and Firefox (plugin technology) which run independently of each other.