href-css-styling.css

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 */
}