From http://www.w3schools.com (Copyright Refsnes Data)

HTML 5 <meta> tag

Definition and Usage

The <meta> element provides meta-information about your page, such as descriptions and keywords for search engines and refresh rates.

Differences Between HTML 4.01 and HTML 5

The scheme attribute is no loinger supported in HTML 5

HTML 5 has a new attribute, charset, which makes it easier to define charset.
In HTML 4.01 you would have to write:
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
but in HTML 5 it is enough to write:
<meta charset="ISO-8859-1">

Tips and Notes

Note: The <meta> tag always goes inside the head element.

Note: Metadata is always passed as name/value pairs.

Note: One, and not more, of these attributes must be defined: charset, http-equiv, name.

Note: The content attribute MUST be defined if the name or the http-equiv attribute is defined. if none of these are defined, the content attribute CANNOT be defined.

Examples

Define keywords for search engines:
<meta name="keywords" content="HTML, DHTML, CSS, XML, XHTML, JavaScript, VBScript" />

Define a description of your web page:
<meta name="description" content="Free Web tutorials on HTML, CSS, XML, and XHTML" />

Define the last revision of your page:
<meta name="revised" content="Hege Refsnes, 6/10/99" />

Refresh page every 5 seconds:
<meta http-equiv="refresh" content="5" />

Attributes

4: indicates if the attribute is defined in HTML 4.01
5: indicates if the attribute is defined in HTML 5

Attribute	Value	Description	4	5
charset	character encoding	Defines the character encoding for the document		5
content	some_text	Defines meta information to be associated with http-equiv or name	4	5
http-equiv	content-type expires refresh set-cookie	Connects the content attribute to an HTTP header	4	5
name	author description keywords generator revised others	Connects the content attribute to a name	4	5
scheme	some_text	Defines a format to be used to interpret the value of the content attribute. Not supported	4

Standard Attributes

class, contenteditable, contextmenu, dir, draggable, id, irrelevant, lang, ref, registrationmark, tabindex, template, title

Try-It-Yourself Demos

Document description
Information inside a meta element describes the document.

Document keywords
Information inside a meta element describes the document's keywords.

Redirect a user
This example demonstrates how to redirect a user if your site address has changed.