Whenever 
Duplex is selected, Canon
Easy-WebPrint prints double-sided. Note that double-sided (duplex) printing
is only available with Internet Explorer 6.0 or higher. If your printer
does not support duplex printing and you select it, you will get a normal
print.
Not all printers support automatic duplex printing even if a duplex option is displayed by the printer driver. Please refer to your printer and/or printer driver documentation for more information.
To choose duplex printing, use the Duplex
toolbar button, or select the More Options
button on the 
Options
dialog.