How can I tell if my case is an ATX or MATX?

Here's a picture of it... http://www.pics.storedby.us/images/85233鈥?/a>How can I tell if my case is an ATX or MATX?
Count up the openings on the back. If there are three or four, you have a MATX, if there are 6 or 7, you have a full ATX, if you have more than 10, recount them, there won't be that many.