There are plenty of specialized directories and you have to pick and choose the best that fit your needs. Hence, we advice you to submit your site to these and spend your money wisely. Also keep in mind it is a good practice to submit your site frequently, since often they drop you from the listing. These are some of the softwares available, that help you rigister with major search engines and in some cases over 100 search engines. Some of the registration services listed above offer you a 'continuous registration' service.
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