Deep Web, is also know as ‘Hidden Web’, ‘Dark Web’, or the ‘Invisible Web’. It is mostly generated by database-driven pages that are usually visible to authorized members. Who can access the hidden information after logging into the system.
Such data is totally hidden from search enging crawlers (or the ‘spiders’), that means Google, Yahoo, MSN, Altavista and other search endinges cannot search data from these pages.
Web crawlers of todays technology can only read ‘surface web‘.