What does P0442 code mean? "Evaporative Emission Control System Leak Detected (Small Leak)" - In a sentence, this is the code recorded in the your car's computer when it sees a small to medium sized leak in the system. Since your evaporative emissions system (You can read more about this at my tutorial for code P0440) is comprised of long hoses, there are many places that it can leak.
The first thing you will want to do is tighten or replace your fuel cap. This is the most common cause of this code.
If that does not fix it then you should open your hood and inspect all hoses for damage.
If you do not find the problem with these methods then it would be best to take your car to a shop that has a "smoke machine". This machine introduces smoke into the system and then it will come out of the same place that the system is leaking. This is BY FAR the best way to fix this problem.
If you still have any unresolved vehicle problems or questions, you can ask an auto mechanic online. For expert answers specific to your vehicle's make and model, I recommend JustAnswer Car. They have a large pool of certified mechanics to answer your questions for a small fee and you can also browse their answers to other users for free.