Seem is used when the quality isn't obvious. If you said "that looks strange", you're saying that whatever you're looking at is definately strange, and there's no arguing about it. "It seems strange" would be used when you think the object is strange, but it isn't obvious, there's doubt involved.

I always seem to look at questions such as this one and confuse myself... I believe if you seem mad it's an educated guess, but if you look mad that's more apparent. She seems mad She looks mad I would feel more comfortable to the one that seems mad. Seems is something you think, and looks is something you see...

I think the difference is "result" and "action".