Focusing the UnityPlayer

We're using Unity 2 with the unity 3.x based browser plugin, and we're having trouble focusing this. I found bits and pieces of information and similar problems, nothing that really helps me.

The problem is, we have a play button that appears when Unity is paused, which appears where Unity would normally be. Clicking this button sets the visibility css property to "visible" (as it was hidden). But then you still need to click on the Unity Player one more time to allow keyboard events through again (ASWD movements).

I've tried setting the webplayer's focus with:

document.getElementById('UnityObject').focus();

It seems to work in IE8, but not in Firefox 3.5 or 3.6 or Chrome 8.

Obviously you could just put the pause button in Unity rather than HTML, so I assume you have a good reason (eg. performance). But you could put the pause button in Unity and use focus/blur events to show/hide the plugin (and have your current HTML button to attract the user to focus).