Basic Meta tags are Keywords & Description that content length should be less than & equal to near about 255 characters.
Keywords Meta tag is used to define keywords of web page.
<meta name="Keywords" content="HTML,PHP,ASP">
Description Meta tag is to used define description of web page.
<meta name="Description" content="IT Help Desk">
Revised Meta tag is used to define last update of web page
<meta name="revised" content="01/11/08" />
Refresh Meta tag used to update web page every 10 seconds.
<meta http-equiv="refresh" content="10" />
Read more.. http://html-meta-tags.blogspot.com/