There's a flag outside my neighbor's house, it looks like a pentagram?

I doubt it. If it wasnt upside down then its a pagan symbol. Pagans are just tree huggers nothing to be worried about.. Just guard your trees..LOL>>

What year is this, 1690? They were probably a bunch of Wiccans casting a circle. Or maybe it was the flag of the country of Morocco. Big deal.

>>What does this mean and should I be concerned?

Yes, you should be concerned that you're getting nervous over something as mundane as a house flag, and gossiping about it to random strangers on the internet instead of actually saying hello to your neighbors.

>>That flag doesn't look friendly...

Well neither does a giant naked Nazarene carpenter nailed on to two pieces of wood.

Umm??? Maybe its the star of david and your neighbors are jews and getting ready for shabbat. Maybe your neighbors are wiccans and are celebrating stuff with their coven.

If it looked like this: http://upload.wikimedia.org/wikipedia/commons/thum...

There jewish.

If it was a pentagram their wiccans.

freedom of religion......as bad as it is

Upon a little research that turns out to be the flag or Morocco

Your neighbors are probably dorks. Probably where the atheists of your state gather together to discuss how to preserve secularism, followed by setting up a guild on WoW.

pentagrams represent earth, water, fire, air and spirit, nothing bad

It means that you should mind your own business.

So what ?

Poop on it.