I'm renovating a bathroom in my home built in 1958 and went to replace a bank of wall switches when I came upon this wiring. I've changed all of the switches and plugs in the rest of the house and haven't come across one wired like this before. All of the switches are connected together on the bottom terminal. Can someone explain to me if this is wired properly, or if it should be rewired? Also, is it possible for me to put change the switch on the far left to a dimmer switch without causing any problems? Thanks!
Basically, the wire that is connected to all of the switches (in parallel) is the HOT wire coming from your circuit breaker/fuse box. The other wire on each switch is going to the load (light or outlet). As @keshlam alluded to in his comment, this is equivalent to the common wire going to a wirenut with separate pigtail wires to each switch.