Yes, all pages will be the same width in any particular Publisher
publication. If you want some pages on your site to be different widths,
then you need to create those pages with a different Pub file. Then you
upload and link those files to your main publication. I prefer creating a
subfolder on the root directory and uploading to that subfolder, but there
are other ways of doing it. Here is an article and another way:
Building a web site with multiple Publisher web publication files:
http://msmvps.com/blogs/dbartosik/archive/2006/01/16/81264.aspx
DavidF