off-site SEO is mostly about the backlinks and this should be the area of the main focus when it comes to ranking. The thing about porn is that it is very hard to get natural links for new websites and people are not going to link to you if you are not popular so webmasters are forced to spend money on backlinks and here you can buy blog posts and trade them with others for free. There are free ways to get them and I mean forums, comments, submissions, but you have to be careful that you do not end up overdoing it because spamming is easy to stop and you will be punished by Google for this.
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How to get Free Backlinks for adult site