In this simulation of ordered lists, the OL is represented by a DIV with a class of "ol" (and has a light gray background), each LI is represented by a P, and each marker is an absolutely left positioned span. The first example shows how this works pretty well: the markers can be large, without messing with auto line-heights, and the non-marker content aligns as expected.

The second example shows that this still works when overflow of the OL is set to visible and its height is reduced. But for some reason, changing the vertical overflow to scrolling also changes the absolutely positioned horizontal overflow to be hidden (even though it was set to be visible).

The third is example is more of a hack, in which padding is used on the OL instead of margin, but that means its background color extends too far to the left.

One can also wonder why padding (or possibly line-height) has been added to the top of the OL in the third and fourth examples.