How to Remove Footers of LaTeX Beamer Templates?

I do not have the most direct answer for you as I do not use the beamerthemesplit template. But for a recent presentation, I was tempted to decompose the themese a little. So if you use this

\mode<presentation>
{
  \useoutertheme{default}   % empty
%  \useoutertheme{infolines}% simple but bland
%  \useoutertheme{split}    % ok if compress option used
%  \useoutertheme{shadow}   % way too much space used -- ok with option 'compress'
  %\useoutertheme{shadow}   
  %\setbeamercovered{transparent} % or whatever (possibly just delete it)
  %\useoutertheme[subsection=false]{miniframes}
}

you get via default a really empty setup. Adding infolines gives you a footer with three parts, you can study the code of that outer theme to just add parts. Likewiese with color themses -- I just experimented a little and eventually went back to a default theme.

I got rid of the default footer, and inserted page numbers instead using the following commands.

%gets rid of bottom navigation bars
\setbeamertemplate{footline}[page number]

%gets rid of navigation symbols
\setbeamertemplate{navigation symbols}{}