Will DDR2 Memory work on a DDR3 Mobo?

Yes... 800 should be all you need.

No, it supports DDR3, not DDR2. Is there a reason what you are looking at getting DDR3? At this point in time, I would get a DDR2 setup. i7 is coming, meaning you'd need to get a new CPU, mobo, and ram when it comes.

NO!!!
That board will only hold DDR3.

If you are buying today, DDR2-800 is cheap.
Look at the DDR2 version of the same board: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Performance differences will be within 1-2%, and it is much cheaper.

NO, you cannot use DDR2 on a DDR3 motherboard. They are pin incompatible. It physically will not fit, unless you like damaging your components. I don't know what vertigo is talking about, but his info is incorrect!

Another one here

NO!
You just CANT! use DDR3 on DDR2

Get the DDR2 version of the motherboard and get some good 800Mhz or 1066Mhz RAM with 4-4-4-12 latencies.

If you Nsist on DDR3, I recommend 1600Mhz and up

Yea, I have to go ahead and agree with 474545b. DDR2 is not support on this board . If I'm not mistaken, they make both DDR2 and DDR3 versions of the x38/48 chipset boards and the GA-X48T-DQ6 is a DDR3 board. This is what I got from searching Google cause I'm not up to par on Intel offerings. Correct me if I'm wrong.

The "T" in the Gigabyte model number indicates DDR3. This is the DDR2 model (GA-X48-DQ6):

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

You might also want to consider an X48 motherboard that accepts both DDR2 and DDR3 (though not at the same time), such as MSI's X48C Platinum.

Hey, thats pretty cool, if someone gets enuf negative votes it hides their post  

As said... NO.

I beleive however, there are/were some boards around with both DDR2+3 slots, meaning u could run either, not both. Not sure if any are still around tho, and as said i7 is coming and for now ddr3 is a total waste of time.