Comment 6 for bug 1115992

But with Offset as a percentage, as it is now, you don't have to worry about where the dock appears when a resolution change happens. It is always in the same vicinity. This behavior is similar to how Alignment works. Right-aligned docks *always* are right aligned, even if I change my resolution. Keeping it as a percentage makes them both behave in the same way, so you can easily just have your dock 'on the left 1/3' etc. Frankly, the Alignment is redundant, as you can specify 0% Offset, -100% Offset, and +100% Offset to get the same effect.

I am highly inclined to remove the Alignment.