\documentclass[a4]{seminar}
\usepackage[german]{babel}

\renewcommand{\familydefault}{\sfdefault}

\begin{document}

\newenvironment{CHslide}[1]
  {\begin{slide}%
     \begin{center}\Large #1\end{center}%
     \vspace{\stretch{1}} }
  {\vspace{\stretch{2}}\end{slide}}

\slideframe{none}

\newpagestyle{footinfo}
  {}
  {\tiny \LaTeX\ leicht gemacht \hspace{\stretch{1}}Einf"uhrung
   \hspace{\stretch{1}}\copyright\ 2002 by Joe User}

\pagestyle{footinfo}

\begin{slide}
  \pagestyle{empty}
  \begin{center}
    {\Large \LaTeX\ leicht gemacht}\\[2mm]
    {\huge Einf"uhrung}\\[15mm]
    {\large Joe User}\\
    {\small \texttt{juser@TechFak.Uni-Bielefeld.DE}}
  \end{center}
\end{slide}

\end{document}
