Hi
Thank you for using Microsoft Windows Vista Forums.
Snipping tool is designed in such a way that we can capture only the items which are visible on the desktop.
However, you can zoom the page to fit in to desktop and use the snipping tool to capture.
Refer the link below for more information on snipping tool.
Use Snipping Tool to capture screen shots
http://windows.microsoft.com/en-US/windows-vista/Use-Snipping-Tool-to-capture-screen-shots
Regards,
KarthiK TP