Say you add some new element to the page and it pushes things around. That can happen instantly, but it helps your brain understand what just happened if the elements that were pushed away animate to their new position. Enter Alex MacCaw and his new magicMove jQuery plugin:
The library works by appending a separate and hidden clone of the element you’re transitioning to the page. Any DOM manipulation you do is actually manipulating that clone. Then, when you’re finished, the library looks at the difference between the element’s current position, and the clone’s position, and animates between them (using CSS transitions).