Search marketers know it's important to stay ahead of online trends when optimizing their content to catch clicks. Google Trends has long offered insight on the queries that dominate Google, and now Yahoo is offering marketers information about the demographic breakdown for hot searches on its sites.

The company announced today that it has launched Yahoo Clues to give a "unique 'behind the scenes' look into the popular trends across the millions of people who use Yahoo to search every day." The feature offers volume charts, demographic breakdowns, maps and related queries when users type in requests to "discover" relevant search data.

Yahoo Clues offers insight into the day's popular search terms on its homepage. A top query at press time is "emma watson haircut." Clicking this search phrase reveals the searches over time for "emma watson haircut," as well as the gender, age, income and location of core searchers. (Perhaps surprisingly, this beauty-related search topic was more interesting to men than women using Yahoo.)

The tool also offers related phrases and a "search flow." The search flow may be especially useful for marketers – Yahoo explains that it predicts the most probable search terms people tried before or after a given query based on search analysis. This could help marketers catch longtail searches and optimize sites accordingly. (On this note, it seems "emma watson photos" was a top previous and subsequent search phrase among her many male fans who use Yahoo, and "emma watson bikini" was a key related phrase for searchers earning between $25K and $50K.)

Yahoo Clues also lets users compare search terms. This could help marketers determine which phrases, products or services are most likely to bring traffic to their sites at a given time.

Of course, the usefulness of Yahoo Clues is dependent on the idea that Yahoo sites are still valuable in the search market (even if results are now powered by Bing). The latest comScore search data indicates that Yahoo is still the No. 2 search engine on the web, but the company saw declines in both explicit and total core searches last month.