You forgot to disconnect the battery when you
took out the alternator? Your 80 Amp main fuse is
probably blown. $5 at any autoparts store, its
the one that is screwed down in the fuse panel
under the hood.

(I did the same thing when I replaced the
alternator on my 98 civic)

Either that, or do you have an alarm? My car
disables the start until i push unlock on the
remote...

t