Yeah, everytime I do a rib pattern, I forget whether I'm supposed to knit my knits or purl my knits. (IE: Do I -- Row1: k1, p1 Row 2: k1, p1...... or is it Row 1: k1, p1 Row 2: p1, k1)??? Doing it the right way will give you a lovely rib pattern. Doing it the wrong way will give you a messy spiderwebby look.
Since I can never remember, I usually end up tearing out a couple of rows when I realize I chose the wrong option LOL I really should write it down somewhere, eh?
(as for which way is correct... I can't remember in order to tell you!)