The Web isn’t kind to new search engines. Several newcomers, including Cuil, SearchWikia, and Searchme, have all debuted and disappeared in short order in recent years. A new challenger, Blekko, which launched today, hopes to avoid their fate by finessing its results in Wikipedia-like fashion.

It’s a method intended to block the low-quality pages that pollute the results of more established competitors, says Rich Skrenta, a cofounder of the company, which has raised $24 million in funding since 2007. “Various bad actors have created the bulk of URLs on the Web today,” Skrenta says. As examples, he sites spam blogs and companies like Demand Media, which pay people small fees to write content designed mainly to rank high in search results.

Blekko also offers filters, dubbed “slashtags”—simple text tags such as “/hotels” or “/politics”—that can be added to the end of a search query to offer improved results for that topic. Those tags can be subject areas but also matters of opinion—adding /liberal yields different results for a politics search than adding /conservative. Certain slashtags are automatically applied when Blekko realizes you are searching on a particular subject.

Searching for “headache cures” on Blekko and comparing the results to the same search on Google shows the benefits slashtags can bring, says cofounder Mike Markson. “Our ‘/health’ slashtag fires automatically and brings up sites written by doctors that you actually want to go to for medical answers, like NIH, WebMD, and NHS,” he says. “Google’s first page of results features Wikihow, about.com, and sites like home-remedies-for-you.com.”

Blekko users can apply to become editors for a slashtag and then collaborate with others to specify which sites should get a boost when that tag is applied. Just like a Wikipedia page, all the edits made to a slashtag are made visible so that any attempt to game the system is obvious to others and can be quickly reversed.

The company’s goal is to attract a community that will create hundreds of thousands of slashtags that can then be automatically used to improve almost any kind of search query. However, at launch, only seven slashtags will automatically be available, a number Blekko hopes to increase quickly as more users contribute. Already, a closed beta test period has seen 8,000 users create around 3,000 slashtags in three months, says Skrenta.

Gabriel Weinberg, founder of a search startup called DuckDuckGo, says that blocking the “spam” sites Skrenta identifies should yield noticeably better results. “I see these pages as a big problem, they’re gaming Google and other search engines and are really just made to carry ads from AdSense [Google’s advertising platform].” Weinberg uses a combination of manual and automatic tools to block certain sites like that from his own search engine’s results. “I haven’t found it difficult to take them out, so I think technically Google could do it, but they may not do so for business or censorship reasons.”

Encouraging a user community to help with the task has potential, he adds. “There’s one precedent, which is SearchWikia,” says Weinberg, referring to a failed search engine launched by Wikipedia creator Jimmy Wales. “They actually did get a community of tens of thousands that contributed millions of edits, so I do think it’s possible.”

Convincing large numbers of people to switch search engines will be difficult, he adds, because force of habit is so strong. But the payoff for gaining even a small fraction of the search market would be large. “It’s the biggest business on the Internet,” says Weinberg. The Interactive Advertising Bureau estimates that in the first half of 2010 some $5.7 billion was spent on advertisements that appear alongside search results alone.

Google has twice experimented with having users fine-tune its search results, but discontinued both ventures. Co-op, launched in 2006, let users add subject tags to pages to help Google search rank more accurately, and SearchWiki, launched in 2008, let users move results for a search up and down the results list to affect the outcome of future searches.

“There was acclaim for these ideas, but only from the tech community,” says Amit Kumar, founder of startup Vurve. Kumar was formerly director of product for Yahoo Search, where he decided not to carry out similar experiments because he thought few users would take part. “It seems Blekko is taking some of those ideas and perhaps making them a little more usable.” Working together on broad subject categories is more attractive than giving feedback for individual search queries or results, says Skrenta.

But Don Turnbull, a search technology consultant and previously director of Outride, a search technology firm bought by Google in 2001, says that although Blekko’s results are competitive with Google’s, it will likely appeal most to early adopters. “People that aren’t search geeks may struggle, although applying slashtags automatically will help with that,” he says. “I know the team is proud of being almost all engineers, but they need to avoid building an interface like a 747 cockpit.”