This is not part of the default WordPress installation. It could be coming from a theme or a plugin. It can also be placed by a …gulp… hacker. First you need to find where it occurs in order to verify what action gets rid of it. This can be easy or challenging. There’s many tricks that can be used to hide it from you. First, log off your site and check pages as a unregistered user. Load likely pages and view/search the source html, looking for hidden links.
You may need to use the view as googlebot feature because the link may only be inserted for search bots. You could also grab a googlebot user agent string off the ‘net and set your browser to use it while exploring your site. If you have terminal access, you could try grepping for part of the link in the filesystem, but this can easily be disguised by hexcoding the string.
You should also scan you site with a site scanner like http://sitecheck.sucuri.net/scanner/ . Good luck.
I used Sucuri SiteCheck and it did not find anything.
