Here the answer read this topic which is briefly explained (http://webmarketer.x88.biz/viewtopic.php?t=17) about what is spider and what are the works to be done for spidering your webpage regularly. I personally experienced and benefited out of this. Try this you will feel the difference.
Spider is a program that automatically discover, download, analyze, and index web pages for its associated search engine. Spiders are used to feed pages to search engines. The name spider because it crawls over the World Wide Web in the process of indexing web pages.
