Search engines want websites to have a level playing field, and look for natural links built slowly over time. While it is fairly easy to manipulate links on a web page to try to achieve a higher ranking, it is a lot harder to influence a search engine with external backlinks from other websites. This is also a reason why backlinks factor in so highly into a search engine's algorithm. Lately, however, a search engine's criteria for quality inbound links has gotten even tougher, thanks to unscrupulous webmasters trying to achieve these inbound links by deceptive or sneaky techniques, such as with hidden links, or automatically generated pages whose sole purpose is to provide inbound links to websites. These pages are called link farms, and they are not only disregarded by search engines, but linking to a link farm could get your site banned entirely.