Simple deltas benefit by trading off computation of the deltas for a reduction in bandwidth and latency over the slow link when both sides store the same old version of a page. Optimistic deltas trade off an increase in the amount of data transferred, by sending an older version during an idle time of the slow link followed by a delta, for a reduction in end-to-end latency. The viability of either form of deltas is thus dependent on ``smallness'' of deltas, which we evaluate in Section 3.1. Optimistic deltas depend additionally upon long idle times on the slow link, which we consider in Section 3.2.