There have been long standing problems with the buttons not working in
Firefox, and now a [further
problem](https://groups.google.com/d/msg/tiddlywiki/GlsruQyPOag/BAhnI2mt
BgAJ) has come to light, and been similarly hard to resolve.
On balance, I’ve decided to remove the undo/redo buttons from the
toolbar (the ctrl/cmd-Z shortcut is still operational), thus avoiding
the problems, and saving some space in the core.
