Sometimes it means that he thought you were super hot, and had to look back. HOWEVER, there have been cases where I was simply looking around, my glance passed over a girl who was looking dead at me, then it registered that she was looking at me and I looked back. I didn't necessarily think she was cute, I just looked back because I was caught off guard by someone staring right at me like that. So don't jump to any conclusions just yet and don't start wishfully thinking because your brain really WANTS him to like you. Make sure you know for sure first! :)
It happens when I'm somewhere and a person I know enters the room (but I wasn't expecting them) so I just skimmed the room, saw them, but didn't register it, so I look again, to make sure I didn't miss anything. And it usually happens that that is the person I know - then we chat or sth.
Or it happens when I like a guy, and am surprised he's there, so in my 'mild shock' I turn my head quickly in his direction to make sure I saw what I just saw, and to make sure it's not just my imagination. . . Haha
it's atrick! Double takes are actually tricky, sometimes it means that he thinks you're pretty, cute or hot and othertines it just accidently happens... however how would we know what the guy really thinks... but just don't take too seriously, my dog double takes at me all the time -.-