摘自wiki：The keywords attribute

Search engines began dropping support for metadata provided by the meta element in 1998, and by the early 2000s, most search engines had veered completely away from reliance on meta elements. In July 2002, AltaVista, one of the last major search engines to still offer support, finally stopped considering them.

No consensus exists whether or not the keywords attribute has any effect on ranking at any of the major search engines today. It is speculated that it does, if the keywords used in the meta can also be found in the page copy itself. With respect to Google, thirty-seven leaders in search engine optimization concluded in April 2007 that the relevance of having your keywords in the meta-attribute keywords is little to none and in September 2009 Matt Cutts of Google announced that they are no longer taking keywords into account whatsoever. However, both these articles suggest that Yahoo! still makes use of the keywords meta tag in some of its rankings. Yahoo! itself claims support for the keywords meta tag in conjunction with other factors for improving search rankings. In Oct 2009 Search Engine Round Table announced that “Yahoo Drops The Meta Keywords Tag Also” but informed us that the announcement made by Yahoo’s Senior Director of Search was incorrect. In the corrected statement Yahoo Senior Director of Search states that “…What changed with Yahoo’s ranking algorithms is that while we still index the meta keyword tag, the ranking importance given to meta keyword tags receives the lowest ranking signal in our system…. it will actually have less effect than introducing those same words in the body of the document, or any other section.