Front Brakes Rattling

Im not really sure what part of them are to blame. When im off them going about 15 mph the rattling is most noticable, but when i step on the brakes they stop rattling.

Anybody know what could casuse this, and how to go about fixing it?

Check the bolts that hold the caliper on. The previous owner of my Jeep took it to Jiffy Lube to get the brakes done and they completely stripped out one bolt and just left it there hand tight!!! I fixed it with a helicoil, tightend it up, and no more rattles.