To prevent users from linking to one version of a URL and others linking to a different version (this could split the reputation of that content between the URLs), focus on using and referring to one URL in the structure and internal linking of your pages. If you do find that people are accessing the same content through multiple URLs, setting up a 301 redirect32 from non-preferred URLs to the dominant URL is a good solution for this. You may also use canonical URL or use the rel="canonical"33 link element if you cannot redirect.
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.
9. Troubleshooting and adjustment. In your first few years as a search optimizer, you’ll almost certainly run into the same problems and challenges everyone else does; your rankings will plateau, you’ll find duplicate content on your site, and you’ll probably see significant ranking volatility. You’ll need to know how to diagnose and address these problems if you don’t want them to bring down the effectiveness of your campaign.