\documentclass[11pt]{article} \usepackage[]{color} \usepackage[letterpaper,colorlinks,breaklinks,backref]{hyperref} %\usepackage{url} %use as alternative to hyperref for testing \newcommand{\myurl}[1]{{\url{{#1}}}} \begin{document} \url{http://www.wmich.edu/mus-theo/etg/et_guide.html} %ok now with hyperref, ok with url \myurl{http://www.wmich.edu/mus-theo/etg/et_guide.html} %fails with hyperref, ok with url \cite{THE} \bibliographystyle{unsrt} \bibliography{testurl}%fails with hyperref, ok with url \end{document}