There are a lot of people asking about how to mute their web browsers and various other applications, so I thought I'd post this. It's not the most practical workaround, but it does work and until browsers begin including mute functionality it's the best we've got.
If you have Audio Hijack you can hijack and re-launch the app you want to mute. Then simply press Audio Hijack's "mute" button. Done.
If you have Audio Hijack you can hijack and re-launch the app you want to mute. Then simply press Audio Hijack's "mute" button. Done.