A one way link is a link from a website that is not linked to from the other site. This is different from a two way link where both websites mutually link to each other. In the early days of search engine technology, the link value was the same regardless of whether it was a one or two way link. However since many people took advantage of this and started using link exchange program to gain alot of links, most search engines started to lower the value of two way links. This is why it is important to gain one way links in order to achieve good rankings.
There are many ways to generate those important links. The best way is to simply have good content on your site. This will generate links from other website owners who will link to your site as a service to their users. These kind of links will not only help you improve your search engine rankings, but can also generate alot of traffic from people following the link.
Another great way to generate backlinks is through web directory submissions. Web directories are big collections of categorized links that help web surfers find the kind of site they are interested in. Perhaps the most well know web directory is the one maintained by Yahoo. While inclusion into most directories is free, some of them have a fee for getting listed.
Writing articles for other websites is another good way to gain links by giving other website owners content in exchange for a link back to your site. If an article is particularly informative it may find it's way to many other sites and generate alot of one way links.
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