/*  HTTP links */
a[href^="http://"]{
    padding-right: 20px;
    background-color:red;
}

/* emails */
a[href^="mailto:"]{
    padding-right: 20px;
    background-color:green;
}

/* pdfs */
a[href$=".pdf"]{
    padding-right: 20px;
    background-color:bue;
}