Many startups have tried to take on the search business in recent years but ultimately failed to steal any significant market away from the usual giants. Unconcerned by the failures of Cuil, Clusty and several others, a small Silicon Valley company with big-name backers is launching a new search engine called Blekko that promises to weed out the ever-proliferating junk and spam sites polluting web results by narrowing searches to groups of websites that people, not computers, have pre-approved as being the best sources of information for particular topics.

Blekko has seven main categories – health, automotive, lyrics, colleges, personal finance, recipes, and hotels. If you search for "investing in bonds," for example, Blekko gives you a good set of results from SmartMoney, MSN's Money Central, and several others. The interesting part is that users can create their own 'slashtags' – sets of web pages covering particular topics – so when these are added to a search query, results are restricted to those from these particular sites. Other users can contribute to the lists of relevant sites for a particular slashtag, if their creator allows it.

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The reasoning behind Blekko's approach is that the web has increasingly become saturated with spam-like websites, specially designed to artificially boost ranking in Google's search results, but whose content is heavier on marketing pitches than substantive information. The company says they're on par with Google and Bing for regular non-slashtag queries, but their aim is to become popular as a secondary search engine for certain types of queries that can be easily filtered by topic. In fact, the team believes Blekko could be profitable with 1 million to 2 million queries a day (out of the over 1 billion now done on the Web) and claim they have no illusions of unseating Google anytime soon.

It's an interesting concept that focuses on quality rather than quantity. We'll see how things develop as more people create and refine slashtags, but perhaps the most difficult part will be getting in users's mind when thinking about search.