Pop the wheel off and look behind the drum.
I'd bet the wheel cyl. is leaking or did leak.
Also look at the inside of the rim. Is it wet? Also most likely the wheel cyl. ( or brake cyl. ) same thing.
My wife and I are the proud owners of a Silver 2000 4-Runner SRS. Woohoo. Thanks for the info guys. Everything is dry, so it may have just been an old stain. SCRunner12- No more pictures of stange people holding dogs. :biggrin2: