Positionable!

Positionable is a developer tool that lets you quickly manipulate elements the way you would in an image editor. Familiar workflows like dragging, nudging, align/distribute, and undo make it simple to place elements exactly where you need them to be. Once you're ready, you can copy styles to the clipboard or save them to disk. Designed for rapid styling, prototyping, working with sprites, etc.

PLEASE POST ISSUES HERE (with demo if possible):
https://github.com/andrewplummer/Positionable/issues

By default, it works on absolute and fixed positioned elements, however you can set a CSS selector to target exactly the elements you're interested in. Static elements will be forced to position "relative".

When working with sprites, you can similarly use both the mouse and keyboard to move the background position. Alternatively, double clicking on the background will detect contiguous sprites and snap the element dimensions and background position to match.

Work with multiple elements by dragging to select or holding SHIFT. All selected elements will move together, and can be aligned or distributed just as in popular image editing software.

Other features like rotation, undo, z-index ordering, and background "peeking" make positioning elements a breeze!