What does a “b” mean in firebug release?

Question

In the firebug release downloads there are many different choices. Many versions have an a or b appended to the name. What does this mean?

For example:

firebug-1.8.0 a3 .xpi

or

firebug-1.8.4 b1 .xpi

Answer 1

Those are alpha and beta versions.

Normally, it is a good idea to stick to the stable releases.