I want to have a webpage as my background/wallpaper on my desktop. Not just
the pictures from the webpage, but actual page which is my calendar.

How can I do this?

From Windows XP Help, searching with the term "active desktop":

To add Web content to your desktop
1.. Right-click a blank area on the desktop, and then click Properties.
2.. On the Desktop tab, click Customize Desktop.
3.. On the Web tab, click New, and then follow the instructions on your
screen.
Notes

a.. You must be connected to the Internet to add active Web content to
your desktop.
b.. To browse Microsoft's Desktop Gallery Web site, in the New Desktop
Item Wizard, click Visit Gallery. The New Desktop Item Wizard opens when you
click New on the Web tab.
c.. To select a different Web site, type the Web site address, or click
Browse to locate it. ...
I want to have a webpage as my background/wallpaper on my desktop. Not just
the pictures from the webpage, but actual page which is my calendar.

How can I do this?