Will DX lenses work on FX bodies?

I have a D3100 Nikon camera, but I'm willing to buy a D800 soon. My question is: will all DX lenses I have work properly with the D800? I know that all FX focal lenses are magnified by x1.5 on DX bodies, so what about DX lenses working on FX cameras?

You'll get a circular image within the full frame. In other words, they will work if you crop a lot, however the D800 has so much resolution, you can probably get away with it. But eventually, You'll want FX lenses. If you can't get new ones, buy old ones and shoot in manual mode.

Sorry, but ^^^ is wrong. If you mount a DX lens on a D800, it automatically goes into a cropped DX mode and shoots at 16MP in a standard rectangular format, using the 1.5x crop factor just as if it was on a DX body.