Apparently, through good indexing from other sites. Keep in mind that ask.com emcompasses askjeeves, ask, teoma and excite and others. It's funny that they say they don't accept paid inclusions anymore, but many of their owned web properties do!
If you don't want to spend any money, make sure you have a robots.txt file and code valid pages, helping other bots find you and as Ask crawls and follow their indicies, they'll eventually find you too.
Taken from
Ask.com
Q: How do I register my site/URL with Teoma so that it will be indexed?
A: We appreciate your interest in having your site listed on Ask Jeeves and the Teoma search engine. It is important to note that we no longer offer a a paid Site Submission program. As a result of some recent enhancements to Teoma, we're confident that we're indexing even more Web pages than ever, and that your site should appear in our Search index as a result of our ongoing "crawling" of the Web for new and updated sites and content.
If you are the owner/webmaster of a site in question, you may also want to research some online resources that provide tips and helpful information on how to best create your Web site and set up your Web server to optimize how search engines look at Web content, and how they index and trigger based upon different types of search keywords.
Q: Why aren't the pages the Teoma crawler indexed showing up in the search results at Teoma.com?
A: If you don't see your pages indexed in our search results, don't be alarmed. Because we are so thorough about the quality of our index, it takes some time for us to analyze the results of a crawl and then process the results for inclusion into the database. Teoma does not necessarily include every site it has crawled in its index.
Good Luck!
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