I have this simple CSS...
div:before { content: \"G\'day\"; filter: alpha(opacity=40); -moz-opacity: .4; opacity: .4; }
I don't think it's possible.
I had the same problem a while back, and I ended up just working around it (by not using :before).
:before
Here's some sound reasoning as to why it's not possible: Why does a filter gradient on a pseudo element not work in IE8?