Website owners should carefully check the reputation of anyone they employ to do search-engine optimisation, says Google engineering director and expatriate New Zealander Craig Nevill-Manning.
Speaking at a workshop at the NZ Comptuer Society's 50th Anniversary Conference in Rotorua yesterday, Nevill-Manning said some employees might be optimising the site for other interests, by slipping in invisible pointers to other sites.
If your site has a good reputation, the fact that yours points to theirs will raise their site’s rank in Google searches, he said.
The Google ranking of a site is based partly on how many other sites of already high rank point to it. Most other search-engine providers use similar ranking algorithms.
“I’ve seen sites like this, where people have employed someone to improve the ranking of their site and they’ve achieved that, but in the process they’ve introduced a whole bunch of other content that points to their own sites,” Nevill-Manning said.
Conversely, the implied association with low-reputation sites may lower the ranking of your own site.
“So if you employ a company to optimise your site, make sure you get recommendations and think carefully,” he said, “because once you give them access they may introduce their own stuff.
“Check the Google cache too; it could be that they only inserted the bad stuff for when the Google-bot crawls the page [removing it afterwards].”
A more usual way of introducing page-rank-raising pointers is by embedding them in comments submitted to the high-reputation site. The effect of this can be nullified by appending a “no-follow” tag to the site’s comments pages, so the Google bot ignores any links in that section.
Google may detect such irregularities, said Nevill-Manning, but ordinarily has no way of notifying the owner. So it’s a good idea to register the site with Google’s Webmaster Central and Google Alerts to establish that contact, he said.
Hackers may manage to alter a site’s data so as to remove it entirely from detection by Google, so it suddenly disappears off the map. One workshop participant testified that he had suffered such an attack. As far as he knew it had been done “just for the hell of it” and without any real nefarious purpose, he said.
The workshop explored ways in which the search-engine ranking of a site may be unintentionally lowered. One piece of advice: avoid references to your site in different ways, say with a www. prefix and without, or the pointers may be counted as references to two different sites. This will halve the reference count Google sees and lower the ranking.
Many of the tricks that make a site visible to Google, such as including textual alt-tags on graphical elements are coincidentally those that make the site more usable for blind and other disabled users, Nevill-Manning said.
The workshop discussed the technique of employing writers to generate articles artificially boosting a site’s reputation. Multiple cut-and-pasted instances of identical text are detected by Google already and discounted, Nevill-Manning says and he hints the company is working on more advanced methods of differentiating useful text from “link-bait”.
Measures taken by Google and other search-engine companies to nullify artificial rank-raising tricks inevitably give rise to new ways of avoiding the fixes, he says. It’s an “arms race” between search-engine operators and disreputable tweakers.
Craig Nevill-Manning is was educated at Canterbury and Waikato Universities. As Google's engineering director, he is based in New York.