i want a ddr3 graphic card but i am not sure that my DDR2 motherboard will support DDR3 please tell me
The Graphics Card's memory interface has nothing to do with your RAM's interface. The only compatibility issues you need to look for is the socket/interface (AGP/PCI/PCI-E/PCE-I 2 etc), and the power requirements which is a PSU problem.
If you can't read or understand your own computer specs then go to your most trusted computer vendor with your computer. He will recommend you what you need to buy.
The ddr3 ram is only integrated to your graphics card, it doesn't have to do anything with ddr2 ram on your motherboard. You only have to determine what slot it may require AGP,PCI,PCI-E these are the most commonly used interface. I'd recommend you to get PCI-E as it has best performence.
give it a try u will come to know tht by yourself