Meta keywords tag was a common practice in SEO for any search engines, but you might not know that it’s been abandoned by most search engines, like Baidu.
Baidu’s engineer LEE, who is in charge of answering questions publicly about SEO, made it clear in August 2012 that meta keywords tag had become a history for Baidu, and Baidu totally ignores it. Here are the screenshots of his words in Chinese during a dialogue with Chinese webmasters: