Mozilla’s Firefox 11 now offers the 3 dimensional page inspector tool that gives the 3d perspective of the page elements in a webpage.You can visually see how the elements are nested with this tool.
Not only 3d view, you can navigate through the page structure ,zoom,pan and rotate the entire structure.Firefox developed it as an extension called as tilt.Now this extension goes to the inbuilt feature starting from firefox 11.The latest firefox aurora comes with this 3d page inspector tool.
To see the 3d view of any webpage you can right click ->inspect element -> click 3D. If you can’t able to see the 3D button on the right corner of the window then it may be due to incompatibility of Web GL.