Target only external links
/* long version */
a[href^="http://"]:not([href*="mysite.com"]),
a[href^="https://"]:not([href*="mysite.com"]),
a[href^="//"]:not([href*="mysite.com"]), {
}
/* shorter version! */
a[href*="//"]:not([href*="mysite.com"]) {
/* external link styles, use :before or :after if you want! */
}
Example from David Walsh
Target specific link types
a[href^="/"], a[href^=".."] {
/* internal relative link */
}
a[href^="mailto:"] {
/* email link */
}
a[href$=".pdf"] {
/* PDF file */
}
See more examples on CSS Tricks