I believe Om Malik was the first to point out that Microsoft has been awarded US Patent #7,415,666, “Method and system for navigating paginated content in page-based increments.” That’s right folks, Microsoft was granted a patent for page up and page down functionality,
A method and system in a document viewer for scrolling a substantially exact increment in a document, such as one page, regardless of whether the zoom is such that some, all or one page is currently being viewed. In one implementation, pressing a Page Down or Page Up keyboard key/button allows a user to begin at any starting vertical location within a page, and navigate to that same location on the next or previous page. For example, if a user is viewing a page starting in a viewing area from the middle of that page and ending at the bottom, a Page Down command will cause the next page to be shown in the viewing area starting at the middle of the next page and ending at the bottom of the next page. Similar behavior occurs when there is more than one column of pages being displayed in a row.
Sheer insanity.