The codes you have are evaporative emission codes. Code P0455 indicates a large evap leak and code P0442 means that a small leak is detected. These codes do not usually cause any problems, but should be looked at. The first thing I would check is to make sure your gas cap is tight and has a good seal. Make sure that you don't fill your gas tank with the car running as well. Filling your gas tank while the car is running will cause these codes too. I would also check for any broken or cracked vapor lines.