Websites are not paged media, so it's not surprising you haven't used @page
The reference for @page is
here.
Note that, for the Cybook/ADE combination, you want top and bottom margins in a @page{} element, but if you want side margins, you better put them in body{}, because page numbers would be affected by page margins (and, if I remember correctly, you have to used a class for the <body>, or the Cybook just uses default margins).