\documentclass{book}
\usepackage[extension=xxx]{hyperref}
\begin{document}
A\footnote{\texttt{abc}}

\href{file://localhost/d:/test2.ps}{foo1}

\href{file://localhost/d:/test2.pdf}{foo2}

\href{d:/test2.pdf}{foo3}

\href{d:/test2.ps}{foo4}

\href{http://www-fourier.ujf-grenoble.fr:80/cgi-bin/zbfr/ZB/math-fr.html?AU=Taylor,+R&format=complete&type=html&maxdocs=10}{weird}

\href{a%b}{hello}

\end{document}