If you think about Search Engine Optimization(SEO), you should think like marketer(offline) to market their product. They should be always and always think as customer. What about SEO? Customer of SEO is search engine not visitor. If you want to get good rank at search engine, you should understand how search engine know your site.

One thing to tell search engine that your site still "live" is with update your content. By updating content regularly, search engine will know your site is live and live.