If (and only if!) Firefox is already running with no tabs open, a call to it from a program, an icon or the command line requesting a particular URL to be open, opens the URL but leaves the focus firmly in the URL bar, despite the fact that the page explicitly and repeatedly (e.g. in a loop, once a second) sets the focus to one of its input fields. This problem does not occur if the Firefox is not already running, or has a tab open (and does not automatically switch to the new tab). The problem also goes away if the page calls alert(). In all other browsers I have access to (IE, Opera, Konqueror, Epiphany, IceApe, Safari) work as one would expect. It's only Firefox that's hogging the focus. To the best of my knowledge, Firefox 6 was fine.

The problem is devastating if the user is used to being able to type a command or a password and hit return. The typed characters get appended to the URL and the result is "page not fuond". :-(