Very important for internet marketing / search engine optimization (SEO). A meta keywords tag provides search engines with a list of keywords that are relevant to a webpage.
This tag has the form: <meta name="keywords" content="SEO, search engine optimisation, SEM..." />
There is some debate in the literature about the importance of the "keywords" meta tag in the ranking of a page. CreatorSEO's experience is that this is an important factor for most search engines as long as the meta keywords relate to the visible content on the page.