I have a canon sd 200 Ixus 30 a tryed to insert a memory car of 2 gb and say error on memory card what it mean

You can see the manual of your camera support size of the memory car, and use the memory card in other place to see if it has some problems.
Here is a article about some memory card problems, wish it's helpful for you

The memory card may need to be formatted. You can do this by plugging the memory card into an sd usb reader (separate purchase) and opening up that drive in your computer right click on the memory card drive and click properties and one of the options should allow you to reformat your card. This will erase any info on the card.