Stylish CSS (Chrome Extends,Firefox Add-on) Display ranking number at 3 Search Engine.

display_ranking_number.css

/* Google */
@-moz-document url-prefix("http://www.google.co.jp/"), url-prefix("https://www.google.co.jp/") {
  body {
    counter-reset: result !important;
  }
  h3.r:before {
    content: counter(result) ". " !important;
    counter-increment: result !important;
  }
}

/* Yahoo */
@-moz-document url-prefix("http://search.yahoo.co.jp/"), url-prefix("https://search.yahoo.co.jp/") {
  body {
    counter-reset: result !important;
  }
  div.hd h3:before {
    content: counter(result) ". " !important;
    counter-increment: result !important;
  }
}

/* Bing */
@-moz-document url-prefix("http://www.bing.com/"), url-prefix("https://www.bing.com/") {
  body {
    counter-reset: result !important;
  }
  div.sb_tlst h3:before {
    content: counter(result) ". " !important;
    counter-increment: result !important;
  }
}