I've made a sub-pixel positioning pixel shader for you all.
It includes an example file.
For those of you who don't know what sub-pixel positioning is: Sub-pixel positioning is a way to make the motion of slow moving, low res objects appear smoother. What it does is it effectively makes it so you can position an object at decimal coordinates (13.5,16.7 for example), and to visually display that, what it does is it sort of bleeds into the adjacent pixels. Just check out the example file, it visually explains it much better than words can.