More meta attibutes for search engines
NOODP
The search engines Google, Yahoo! and MSN use in some cases the title and abstract of the Open Directory Project (ODP) listing of a web site for the title and/or description (also called snippet or abstract) in the search engine results pages (SERPS). To give webmasters the option to specify that the ODP content should not be used for listings of their website, Microsoft introduced in May 2006 the new “NOODP” value for the “robots” element of the meta tags. Google followed in July 2006 and Yahoo! in October 2006.
The syntax is the same for all search engines who support the tag.
<META NAME=”ROBOTS” CONTENT=”NOODP”>
Webmasters can decide if they want to disallow the use of their ODP listing on a per search engine basis
Google: <META NAME=”GOOGLEBOT” CONTENT=”NOODP”>
Yahoo! <META NAME=”Slurp” CONTENT=”NOODP”>
MSN and Live Search: <META NAME=”msnbot” CONTENT=”NOODP”>
NOYDIR
Yahoo! also used next to the ODP listing the content from their own Yahoo! directory but introduced in February 2007 a meta tag that provides webmasters with the option to opt-out of this.
Yahoo! Directory titles and abstracts will not be used in search results for their pages if the NOYDIR tag is being added to a web page.
<META NAME=”ROBOTS” CONTENT=”NOYDIR”>
<META NAME=”Slurp” CONTENT=”NOYDIR”>
Robots-NoContent
Yahoo! also introduced in May 2007 the “class=robots-nocontent” tag. This is not a meta tag, but a tag, which can be used throughout a web page where needed. Content of the page where this tag is being used will be ignored by the Yahoo! crawler and not included in the search engine’s index.
Examples for the use of the robots-nocontent tag:
<div class=”robots-nocontent”>excluded content</div>
<span class=”robots-nocontent”>excluded content</span>
<p class=”robots-nocontent”>excluded content</p>
Academic studies
Google does not use HTML keyword or metatag elements for indexing. The Director of Research at Google, Monika Henziger, was quoted (in 2002) as saying, “Currently we don’t trust metadata”. Other search engines developed techniques to penalize web sites considered to be “cheating the system”. For example, a web site repeating the same meta keyword several times may have its ranking decreased by a search engine trying to eliminate this practice, though that is unlikely. It is more likely that a search engine will ignore the meta keyword element completely, and most do regardless of how many words used in the element.