Yahoo! has introduced a new tag that lets site owners make their core content more visible in search results.

The robots-nocontent tag allows webmasters to define areas of a page that are merely navigational elements or other secondary constructs that should be ignored by search spiders.

Crawlers often index the entire content of a page, which can reduce the prevalence of the main material in queries.

Yahoo!’s idea emerged from discussions at last month’s Search Engine Strategies conference in New York, when engineers heard calls from designers to block out non-essential portions of pages in search results.

The tag should be written as a HTML class – for example, . This text would be visible to humans but rendered invisible in search queries.

“We’re rolling out an index update tonight for this change,” wrote Yahoo! Search’s Priyank Garg yesterday. “As usual, you’ll see some changes in ranking along with shuffling of the pages that are included in the index.”