I found two errors, the above code doesn't work in IE.
First, I don't have all the icons displayed so when the following tries to run
I receive an "Invalid Argument" error in IE (it worked fine in Firefox for some reason).
By changing the code to the following the icon displays correctly.
Second, the onclick function doesn't execute in IE. Apparently the setAttribute function doesn't work correctly with IE in certain situations. By changing the setAttribute line to the following now everything looks & works correctly in FF & IE.