If you use \pagestyle{empty}
and you find some pages are
numbered anyway, you are probably encountering one of the style
decisions built into the standard LaTeX classes: that certain
special pages should always appear with \pagestyle{plain}
,
with a page number at the center of the page foot. The special pages
in question are those (in article class) containing a
\maketitle
, or (in book and report classes)
\chapter
or \part
commands.
The simple solution is to reissue the page style after the command, with effect for a single page, as, for example (in article):
\maketitle \thispagestyle{empty}
\chapter{foo bar} \thispagestyle{empty}
A similar technique doesn't work for a book or report
\part
command pages. For that, and for other detail, take look
at “getting rid of page numbers”.