Why was the Battle of Trafalgar so significant of a loss for Napoleon?

Above all, the British victory at the naval Battle of
Trafalgar kept Napoleon from enacting any future plan to invade the British Isles.
Napoleon had hoped that the combined Franco-Spanish fleet would be able to break
England's longstanding blockade of the French coast. Once Napoleon had control of the
English Channel, he hoped to mount an invasion force against the British, though he had
apparently canceled these plans before the naval battle took place. The Royal Navy,
under the command of the daring Admiral Horatio Nelson, destroyed two-thirds of the
enemy vessels without losing a single ship of their own. The Battle of Trafalgar, though
a decisive British victory that made an everlasting hero of Nelson, did not mean the end
of the French navy, however. Napoleon immediately began a new shipbuilding program, and
the British--still maintaining a blockade along the French coast--watched anxiously as
Napoleon's navy grew larger and stronger. In the end, Napoleon's defeats on land put an
end to any chance of the French navy ever gaining superiority over the Royal Navy--or of
ever invading England.