What does charging is not supported with this accessory mean?

When I charge my Ipod touch 4g on my computer or the wall it sometime says "
charging is not supported with this accessory". EVEN ON My moms IPHONE 4 it also says "
charging is not supported with this accessory"… Help! Does this also mean Virus? OR used the wrong Charger? Help Please Thanks

Added (1). What do I do to get this remove?

When a devise says this, it means either the devise is too over date or out dated for the charger. Also, the computer may be too old for your iPod touch. I have the problem when I plug my iPhone 4S in my car charger. It's defiantly not a virus.

It means the USB charger you're using is supplying either too much or not enough current.

It means the charger you are trying to sue is not compatible. It may or may not charge anyway depending on the charger, but in any case it's not advisable to try and force it.

Buy a compatible charger either a cheaper alternative like this [1] or the official Apple charger.