How can I remove the navigation bar of sections and subsections on the top of each slide generated from a beamer latex file?
I'm using the package beamerthemesplit.
Beamer has different themes you can use, some of which include that navigation bar and some of which don't. The default theme, for example, doesn't include any navigation bar. All the themes available with Beamer are described in the user guide; just pick one that suits your requirements and use it:
\usetheme{default}
for example.
If you want to alter an existing theme to remove the navigation bar, you can try setting
\useoutertheme{default}
and see if that gives you a look you like. If not, you'll probably have to get into some theme-specific manipulations. The information needed to do this is in the user guide I linked to above.