hi, What is search engine spider? what is no follow? What is the combination between two.... please give your suggestion........
Search engine spider or web crawler - A web crawler (also known as a web spider, web robot) is a program or automated script that browses the World Wide Web in a methodical, automated manner. This process is called web crawling or spidering. Many sites, in particular search engines, use spidering as a means of providing up-to-date data. Web crawlers are mainly used to create a copy of all the visited pages for later processing by a search engine that will index the downloaded pages to provide fast searches. Crawlers can also be used for automating maintenance tasks on a website, such as checking links or validating HTML code. Also, crawlers can be used to gather specific types of information from Web pages, such as harvesting e-mail addresses (usually for spam). nofollow is an HTML attribute value used to instruct some search engines that a hyperlink should not influence the link target's ranking in the search engine's index. It is intended to reduce the effectiveness of certain types of search engine spam, thereby improving the quality of search engine results and preventing spamdexing from occurring in the first place. source: wiki
Even long before the concept of no follow links was introduced on the web, the robots or crawling systems were actively crawling and scanning the websites contents and counting the links. The no follow links matter is relatively a new topic in the SEO world and is good for blocking spam originated posts on some sites.