CSS Firefox and IE Issues

So what the french toast. When did Firefox demand that padding errors need to be explicitly stated? I don't understand the thinking behind this. Maybe I am forgetting the past, but does ever child element need to have an explicit statement saying padding:0; ? It seems extremely redundant - but that's what I had to do today. Now I was working with un-ordered lists and no I don't feel like testing this on divs, but i found it very strange that I had to explicitly state that padding must be 0 in ordered to get elements to line up. Now if this was just IE I'd get it, but Firefox 19.0.0 was punishing my ever move.