function extlinkAttach(context) {
  // Strip the host name down, removing subdomains or www.
  var host = window.location.host.replace(/^(([^\/]+?\.)*)([^\.]{4,})((\.[a-z]{1,4})*)$/, '$3$4');
  var subdomain = window.location.host.replace(/^(([^\/]+?\.)*)([^\.]{4,})((\.[a-z]{1,4})*)$/, '$1');

  // Determine what subdomains are considered internal.
  if (Drupal.settings.extlink.extSubdomains) {
    var subdomains = "([^/]*)?";
  }
  else if (subdomain == 'www.' || subdomain == '') {
    var subdomains = "(www\.)?";
  }
  else {
    var subdomains = subdomain.replace(".", "\.");
  }

  // Build regular expressions that define an internal link.
  var internal_link = new RegExp("^https?://" + subdomains + host, "i");

  // Extra internal link matching.
  var extInclude = false;
  if (Drupal.settings.extlink.extInclude) {
    extInclude = new RegExp(Drupal.settings.extlink.extInclude.replace(/\\/, '\\'));
  }

  // Extra external link matching.
  var extExclude = false;
  if (Drupal.settings.extlink.extExclude) {
    extExclude = new RegExp(Drupal.settings.extlink.extExclude.replace(/\\/, '\\'));
  }

  // Find all links which are NOT internal and begin with http (as opposed
  // to ftp://, javascript:, etc. other kinds of links.
  // When operating on the 'this' variable, the host has been appended to
  // all links by the browser, even local ones.
  // In jQuery 1.1 and higher, we'd use a filter method here, but it is not
  // available in jQuery 1.0 (Drupal 5 default).
  var external_links = new Array();
  var mailto_links = new Array();
  $("a:not(." + Drupal.settings.extlink.extClass + ", ." + Drupal.settings.extlink.mailtoClass + ")", context).each(function(el) {
    try {
      var url = this.href.toLowerCase();
      if (url.indexOf('http') == 0 && (!url.match(internal_link) || (extInclude && url.match(extInclude))) && !(extExclude && url.match(extExclude))) {
        external_links.push(this);
      }
      else if (url.indexOf('mailto:') == 0) {
        mailto_links.push(this);
      }
    }
    // IE7 throws errors often when dealing with irregular links, such as:
    // <a href="node/10"></a> Empty tags.
    // <a href="http://user:pass@example.com">example</a> User:pass syntax.
    catch(error) {
      return false;
    }
  });

  if (Drupal.settings.extlink.extClass) {
    // Apply the "ext" class to all links not containing images.
    if (parseFloat($().jquery) < 1.2) {
      $(external_links).not('[img]').addClass(Drupal.settings.extlink.extClass).each(function() { if ($(this).css('display') == 'inline') $(this).after('<span class=' + Drupal.settings.extlink.extClass + '></span>'); });
    }
    else {
      $(external_links).not($(external_links).find('img').parents('a')).addClass(Drupal.settings.extlink.extClass).each(function() { if ($(this).css('display') == 'inline') $(this).after('<span class=' + Drupal.settings.extlink.extClass + '></span>'); });
    }
  }

  if (Drupal.settings.extlink.mailtoClass) {
    // Apply the "mailto" class to all mailto links not containing images.
    if (parseFloat($().jquery) < 1.2) {
      $(mailto_links).not('[img]').addClass(Drupal.settings.extlink.mailtoClass).each(function() { if ($(this).css('display') == 'inline') $(this).after('<span class=' + Drupal.settings.extlink.mailtoClass + '></span>'); });
    }
    else {
      $(mailto_links).not($(mailto_links).find('img').parents('a')).addClass(Drupal.settings.extlink.mailtoClass).each(function() { if ($(this).css('display') == 'inline') $(this).after('<span class=' + Drupal.settings.extlink.mailtoClass + '></span>'); });
    }
  }

  if (Drupal.settings.extlink.extTarget) {
    // Apply the target attribute to all links.
    $(external_links).attr('target', Drupal.settings.extlink.extTarget);
  }

  if (Drupal.settings.extlink.extAlert) {
    // Add pop-up click-through dialog.
    $(external_links).click(function(e) {
     return confirm(Drupal.settings.extlink.extAlertText);
    });
  }

}

Drupal.behaviors.extlink = function(context){
  extlinkAttach(context);
}