a(href^="http://") ( /* fully valid URL, likely external link */ ) a(href="http://google.com") ( /* link to specific website */ ) a(href^="/"), a(href^="… ") ( /* internal relative link */ ) a(href^="mailto:") ( /* email link */ ) a(href$=".pdf") ( /* PDF file */ ) a(href$=".doc") ( /* Microsoft Word document */ ) a(href$=".mp3") ( /* Music file */ ) a(href$=".zip") ( /* Archive file */ )