CSS – File format-dependent link styles

                                          /* external linksThe ^= specifies that we want to match links that begin with the http://*/a[href^="http://"] {
    padding-right: 20px;
    background: url("external.gif") no-repeat center right;
}
 /* emailsThe ^= specifies that we want to match links that begin with the mailto:*/a[href^="mailto:"] {
    padding-right: 20px;
    background: url("email.png") no-repeat center right;
}
 /* pdfsThe $= specifies that we want to match links whose hrefs end with ".pdf".*/a[href$=".pdf"] {
    padding-right: 20px;
    background: url("pdf.png") no-repeat center right;
}
/* zipSame as above but for zip files and it adds an icon at the right of the link. Therefore the :after*/a[href$=".zip"]:after {
    content: url("icons/zip.png");
}