If it's a 2 prongs plug it should not matter unless your are plugging something that is not "Isolated" (Meaning that there is no transformer in it's power supply) and then you add another thing to the inverter outlet and somehow connect those 2 apparatus together.
Example: You have a portable TV that is only built to work on household current. You plug this hing up to the inverter. You connect your car computer power supply (House computer supply) to your inverter. You then use the TV-OUT from your computer to the TV - You have a 50% chance of blowing something up as TV chassis are not usually isolated from the main current as it cost to much for the manufacturer to use a power transformer in the power supply.
Depending on your inverter, unplug everything at its outlet. Get a household lamp and connect it in the inverter to test, is it working?
Best of luck to you
Originally Posted by wonderworm