You have incorrectly wired your 18S20. See figure 4 on page 6 of the manual
for the DS18S20. The Ground and Vcc pins need to be shorted together and
connected to ground. The Data pin goes to the digital pin on the Arduino as
well as thru a 4K7 resistor to Vcc.
The diagram on stuff.nekhbet.ro is not completely correct.
-Rusty-