I've added a muting string feature. To use it, you must be recording a chord. When you press the "Record Chord" button, a "Start Muting Strings" Button will appear. When you press that, any string you press will appear muted in the guitar tab printout. Also, the muted string will appear on the fretboard with an "X" through the image.
To handle a performance issue with every browser but Firefox 1.5, I had to revert to the previous icons for the fretboard. If you want to number the fretboard, there is a button on the bottom that does this for you called "Playback Tab". This will progress through your tab, replacing dots with numbers. Also, using the old way means that the fretboard can get messy, depending on how much you change it. To clean it up, press the "Refresh Fretboard" button.
If you want the best performance for this particular app, I recommend using FireFox 1.5