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iamlost - 9:00 pm on Mar 27, 2006 (gmt 0)
Metadata - Web Access Centre [rnib.org.uk] Note: this is why 'keywords' especially should be few and explicit to the page. No general re-iteration of the dictionary or generic 'all my sites keywords on every page'. And why a good 'description' is valuable beyond directory or SE snippets. Metadata (tags) have not lost relevance simply because one or more SEs discounts/ignores one or another.
Re - your second question of meta tags generally:
...metadata provides important contextual information for people navigating your site, especially those with screen readers who rely on things such as page titles, structured page headings, and lists.