Venice is without doubt one of the most beautiful and popular cities
in the world and you'll find many bed and breakfast or hotels to
stay. Of course you'll probably get your reservations online. You
must be very careful, and check if the hotel/B&B site has proper
pictures displaying the rooms conditions, a good description of
services, and where exactly it is located, if is nearby the center
or at least nearby a train/bus station.
That said, you won't have many problems finding good places to
stay. Just be careful not to spend too much... unless, you really
want to pass one night in those super-luxurious suites with a view
on the "Laguna"!