It's nitpicky* (let's come back to that in a second), but it's time we all learn that there is no such word as "alright". It's always two words: all right. The great news is that there is no confusing rule to remember when to use alright and when to use all right, unless you can't remember that the former is totally incorrect 100% of the time!
*Back to nitpicky, it's a pretty common phrase, but have you really stopped and wondered where it comes from? According to sources I came across, it refers to picking nits (yes, the eggs of lice) out of hair. That's a tedious and meticulous job (as any mother with kids who have lice can attest), just as to nitpick in the figurative sense is to find fault or analyze in an overly critical way. http://www.worldwidewords.org/qa/qa-nit1.htm Similarly, I've heard it originated from chimps who spend much of their time laboriously picking nits from each other's hair. Gross and yet so interesting.