The :even and :odd pseudoselectors seem to select the opposite of what I would expect. I stepped through the code, and the apparent reason is that the jQuery code evaluates an element as even if its index within the jQuery object is evenly divisible by two. Since these indices begin at zero, the first, third, fifth and so on elements in the list (in natural counting order, beginning with one) are considered even. I would consider this a bug, since I think it is the opposite behavior from what most people would expect.