example14.tex

\documentclass{article}
\usepackage{lipsum}
\usepackage{boxedminipage}
\usepackage{fancyhdr, extramarks}
\fancyhead[R]{\leftmark}
\pagestyle{fancy}

\begin{document}
\section{Introduction}

\begin{boxedminipage}{\textwidth}
This is example 14 in the fancyhdr documentation.\\
\textbf{Problem: The header  is the LAST section title, not the first one.}\\
This demonstrates that \verb|\leftmark| uses the \textbf{last} mark on the page, which sometimes isn't nice. This can be solved by using the \texttt{extramarks} package and the command \verb|\firstleftmark|.
\begin{verbatim}
\usepackage{extramarks}
 . . .
\fancyhead[R]{\firstleftmark}
\end{verbatim}
\end{boxedminipage}

\subsection{The Problem}
\label{sec:problem}

\lipsum[1]

\subsection{Evaluation}

\lipsum[2]

\section{Another section}

Some more text.

\newpage
\fancyhead[R]{\firstleftmark}

\section{Introduction}

{\bfseries Solution: Use \verb+\firstleftmark+\verb+: \fancyhead[R]{\firstleftmark}+}

\subsection{The Problem}

\lipsum[1]

\subsection{Evaluation}

\lipsum[2]

\section{Another section}

\lipsum[3-5]

\end{document}