Inbound links pointing to your site are taken into consideration as a part of the search engine ranking algorithms. Inbound links are what convey that your site is (or isn’t) a trusted source. As the search algorithms have become more complex, it’s the quality of inbound links that matters as opposed to the quantity.
When getting started with an SEO campaign it’s recommended to conduct a full SEO link audit, which is the process of pulling the inbound link data of your site and of your competitors using an SEO tool like SEOMoz.
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