The bookmarklet simply applies a layout grid image to the body of the page.
Bookmarklet Source Code:
javascript%3Avoid%28myDiv%3Ddocument.getElementById%28%27_grid_div_mrb%27%29%29%3Bvoid%28myBody%3Ddocument.getElementsByTagName%28%27body%27%29%255B0%255D%29%3Bif%28myDiv%21%3Dnull%29%7Bvoid%28myBody.removeChild%28myDiv%29%29%3B%7Delse%7Bvoid%28myDiv%3Ddocument.createElement%2520%28%27div%27%29%29%3Bvoid%28myDiv.id%3D%27_grid_div_mrb%27%29%3Bvoid%28myDiv.style.background%3D%27url%28http%3A//www.andybudd.com/images/layoutgrid.png%29%27%29%3Bvoid%28myDiv.style.position%3D%27absolute%27%29%3Bvoid%28myDiv.style.width%3DmyBody.offsetWidth+%2520%27px%27%29%3Bvoid%28myDiv.style.height%3DmyBody.offsetHeight+%27px%27%29%3Bvoid%28myDiv.style.top%3D%270%27%29%3Bvoid%28myDiv.style.left%3D%270%27%29%3Bvoid%28myBody.appendChild%28myDiv%29%29%3B%7D
