In a move aimed at taking the search engine giant closer to what's commonly called the Deep Web, Google Inc. Friday said that it has started experimenting to find ways for its search engine to index HTML forms like drop-down boxes and select menus.

Over the past few months, Google has been trying out some HTML forms to see if they could discover Web pages that otherwise couldn't be found or indexed for users, noted Googlers Jayant Madhavan and Alon Halevy, members of the Crawling and Indexing team.

"For text boxes, our computers automatically choose words from the site that has the form; for select menus, check boxes, and radio buttons on the form, we choose from among the values of the HTML," they noted in a blog post. "Having chosen the values for each input, we generate and then try to crawl URLs that correspond to a possible query a user may have made. If we ascertain that the Web page resulting from our query is valid, interesting and includes content not in our index, we may include it in our index much as we would include any other Web page."

If a site includes tools for preventing being crawled by a search engine, Google will adhere to those instructions, it said. In addition, Google will omit any forms that require password input or that use terms commonly associated with personal information like logins or user IDs.

The Web pages discovered using the enhanced crawling method will not come at the expense of the regular Web pages that are already part of the crawl, so this methodology won't impact page ranking, Google noted.

"This experiment is part of Google's broader effort to increase its coverage of the Web," Google noted. "In fact, HTML forms have long been thought to be the gateway to large volumes of data beyond the normal scope of search engines. The terms Deep Web, Hidden Web, or Invisible Web have been used collectively to refer to such content that has so far been invisible to search engine users. By crawling using HTML forms, we are able to lead search engine users to documents that would otherwise not be easily found in search engines, and provide Web masters and users alike with a better and more comprehensive search experience."