Monday, 22 April 2013

Meta Tag in HTML5


Meta elements provide information about a given Web page, most often to help search engines categorize them correctly. They are inserted into the HTML document, but are often not directly visible to a user visiting the site or, Metadata is information about data. The <meta> tag provides metadata about the HTML document. Metadata will not be displayed on the page, but will be machine parsable. The HTML <meta> tag is used for declaring metadata for the HTML document. Metadata can include document description, keywords, author etc. It can also be used to refresh the page or set cookies. The meta tag is placed between the opening/closing <head> </head> tags. 
Attributes
HTML tags can contain one or more attributes. Attributes are added to a tag to provide the browser with more information about how the tag should appear or behave. Attributes consist of a name and a value separated by an equals (=) sign, with the value surrounded by double quotes.
 
There are 3 kinds of attributes that you can add to your HTML tags: Element-specific, global, and event handler content attributes.

Element-Specific Attributes

The following table shows the attributes that are specific to this tag/element.
Attributes Introduced by HTML5
AttributesValueDescription             
Nameauthor, description
keywords, generator
revised, others
Provides a name for the information in the content attribute.
contenttextSpecifies the content of the meta information
http-equivcontent-type, content-style-type
expires
set-cookie
others
Provides an HTTP header for the information in the content attribute.

Global Attributes

The following attributes are standard across all HTML 5 tags.
HTML5 Global Attributes
accesskeydraggablestyle
classhiddentabindex
dirspellcheck 
contenteditableidtitle
contextmenulang 

Event Handler Content Attributes


Here are the standard HTML 5 event handler content attributes.
onabortonerror*onmousewheel
onblur*onfocus*onpause
oncanplayonformchangeonplay
oncanplaythroughonforminputonplaying
onchangeoninputonprogress
onclickoninvalidonratechange
oncontextmenuonkeydownonreadystatechange
ondblclickonkeypressonscroll
ondragonkeyuponseeked
ondragendonload*onseeking
ondragenteronloadeddataonselect
ondragleaveonloadedmetadataonshow
ondragoveronloadstartonstalled
ondragstartonmousedownonsubmit
ondroponmousemoveonsuspend
ondurationchangeonmouseoutontimeupdate
onemptiedonmouseoveronvolumechange
onendedonmouseuponwaiting

For example 
Content Attribute 
The required content attribute specifies the content of the meta information. The value of the content attribute depends on the value of the name or http-equiv attribute.
<html>
<head>
<meta name="description" content="About article" />
<meta name="keywords" content="C#,asp.net,vb.net,sqlserver" />
<meta name="author" content="Rohatash" />
<meta http-equiv="content-type" content="text/html;charset=UTF-8" />
</head>
<body>
</body>
</html>
  
Name Attribute 
The name attribute provides a name for the information in the content attribute. The value of the name attribute depends on the value of the content attribute. If the http-equiv attribute is set, the name attribute should not be set.
<html>
<head>
<meta name="description" content="About article" />
<meta name="keywords" content="C#,asp.net,vb.net,sqlserver" />
<meta name="author" content="Rohatash" />
</head>
<body>
</body>
</html> 
http-equiv attribute 
This attributes Provides an HTTP header for the information in the content attribute. The following example demonstrates how to use the <meta> tag to redirect to another web page.
<html>
<head>
<title>Meta Refresh Example</title>
<meta http-equiv="refresh" content="4;url=http://www.vbdotnetheaven.com/" />
</head>
<body style="background-color:#ff9900;">
<p>Watch me redirect to another page in 4 seconds...</p>
</body>
</html>

Internet Explorer

eq1.gif

Figure1

After 4 seconds this page will be redirected to vbdotnetheaven.com.

eq2.gif

Figure2

Fire Fox  

eq3.gif

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