I know that any light spell of an equal level or higher than a darkness subtype spell will counter and dispel the latter spell. But that's not terribly explained to my recollection.
There's a 3.0 FAQ response from WOTC clarifying that slow dispels haste, no caster level check, no save, no SR, just "this spell unmakes that spell", but I can't find anything on it in the rules.
And actually, there's not a heck of a lot on it in the 3.x rules, either.