[bharath kumaran]

1. Title Tag: <title>The title of the Page</title> (Unique title for your page)
Limit: Google typically displays the first 50-60 characters of a title tag, or as many characters as will fit into a 512-pixel display.

2. Description Tag: <meta name = "Description" Content="Description of the Page">
Limit: Roughly 155 Characters

3. Keyword Tag: <meta name="Keyword" Content="Your Keywords">

According to Google they didn't look at meta keywords then you will be surprised that why I am mentioning it here. It is here because 'Yahoo' search still use these in their SERP. So don't miss it because still have 28% search share so why miss these 28%.

4. Robots Tag: <meta name="robots" Content="......, ......">
The valid values for Robots Meta Tags 'Content' attribute are: "INDEX", "NOINDEX", "FOLLOW", "NOFOLLOW".
Examples are:
META NAME=”ROBOTS” CONTENT=”NOINDEX, FOLLOW”
META NAME=”ROBOTS” CONTENT=”INDEX, NOFOLLOW”
META NAME=”ROBOTS” CONTENT=”NOINDEX, NOFOLLOW”
META NAME=”ROBOTS” CONTENT=”NOARCHIVE”
META NAME=”GOOGLEBOT” CONTENT=”NOSNIPPET”
NOINDEX – prevents the page from being included in the index.
NOFOLLOW – prevents Googlebot from following any links on the page. (Note that this is different from the link-level NOFOLLOW attribute, which prevents Googlebot from following an individual link.)
NOARCHIVE – prevents a cached copy of this page from being available in the search results.
NOSNIPPET – prevents a description from appearing below the page in the search results, as well as prevents caching of the page.
NOODP – blocks the Open Directory Project description of the page from being used in the description that appears below the page in the search results.
NONE – equivalent to “NOINDEX, NOFOLLOW”.