In the properties panel it used to tell me the size of objects.
I seem to have lost this part to the panel. All the other stuff is these, just the size bit.
How do I get it back?
That's odd. What version of Fireworks and what operation system are you using?
Have you tried the basic fixes like quitting and reopening the application, or shutting down and restarting your computer? Do those have any effect on the problem, or is it a permanent thing?
Have you tried using the Info panel to view this information?