here's what: what do you summarize as meta tags, do you mean only meta tags or everything in
<head>
your HTML? careless definition of meta tags mainly includes these elements.
these meta tags are still very important for effective SEO.
<title></title> (actually not a meta tag, but in the <head> section), because Google uses it (in most cases) as the listing header in SERP
<meta rel="description" content="because google uses this text here as the snippet text of the SERP (in most cases) list">
<meta content='noindex, nofollow, noarchive, nosnippet' name='robots'/>
very effective directive to control indexing behavior (and, to some extent, to workaround and value distribution) google
<meta name="robots" content="noodp">
get rid of fragments that use http://www.dmoz.org/ to describe
<meta name="robots" content="noimageindex">
advises Google not to index images found on this page (but they may be indexed if used on other pages)
<link href='http://www.example.com/en/vienna/cha-no-ma' rel='canonical' />
(not meta, but in the head) report the canonical URL (the one you want to index) to the search engines.
<link href="http://www.example.com/en/vienna/b/billa" hreflang="en" rel="alternate" />
along with a canonical cool way to transfer alternative language versions of a page on google
<link href='http://microformats.org/profile/hcard' rel='profile' />
if you want to get rich snippets on google using microformats, these meta-information is necessary.
<META http-equiv="Content-Type" CONTENT="text/html; charset=iso-8859-1">
specifying content type and encoding
<META NAME="google-site-verification" CONTENT="+nxGUDJ4QpAZ5l9Bsjdi102tLVC21AIh5d1Nl23908vVuFHs34="/>
way to check your site for google webmaster tools
which is not important:
meta keyword tag, just forget about it. it's useless (and if you put spam words in it even a negative value)