The user needs needs to re-arrange the layout of modules on a web page directly with the mouse.
Drag and drop has been a common feature on desktop applications for many years. It is only recently that it has found its way to the web. There are a host of new web sites that attempt to bring the desktop to the web. These webtops usually implement drag and drop in order to re-arrange modules around the “desktop” within a browser page.
Recently, we added drag and drop support to My Yahoo!. We spent a good deal of time doing user research and refining our drag and drop library in the process. The result of that research and experimentation has been documented in this pattern.
The pattern can be found at: Drag and Drop Modules.