HTML Tag Attributes

In HTML, tags can have their own attribures a key value pair inside element start tag. You can think of an attribute as a piece of code attached to a tag which supplies additional information. The attribute always consists of attribute name with equal sign (=) and the value of the attribute which is enclosed in quotes, even if the attribute is a boolean attribute.

Example

<p id="elementSection" align="left">Adding content 
of paragraph element.</p>

<img src="image.gif" alt="This attribute will 
display when mouse over on this image."/>

In HTML, attributes are very useful when you want to perform some operation with the help of javascript or apply some visual effects using CSS on HTML element. Let's assume that if you want to change text color when mouse over your paragraph or change the image size when mouse over the image. You can achieve this by attaching attribute to the elements.

Example

<!DOCTYPE html>
<html>
<TITLE>HTML Attribute Example Code</TITLE>
<HEAD>
<SCRIPT LANGUAGE="JavaScript">
function stext() {
		var x = document.getElementById("div1");
		var y = document.getElementById("div2");
		x.style.color = 'red';
		y.style.color = 'black';
	}

	function htext() {
		var x = document.getElementById("div1");
		var y = document.getElementById("div2");
		x.style.color = 'black';
		y.style.color = 'red';
	}
</SCRIPT>
</HEAD>

<body>
<span id="div1" style="color:black;" onmouseover="stext()" 
onmouseout="htext()">www.techstrikers.com</span><p />
<hr color="black" />
<span id="div2" style="color:red;" onmouseover="htext()" 
onmouseout="stext()">www.techstrikers.com</span> 

</body>
</html>

In above example "id" attribute is using javascript to access the element and perform text color operation on span element.

See Live Example

HTML Tag Common Attributes List

The below table contains complete list of commomnly used attributes and their description which is supported by HTML version.

Attribute Name	Attribute Description
Id	This events will encounter when page loads.
Alt	This events will encounter when page loads.
Class	This events will encounter when page unloads.
Style	This events will encounter when page loads.
Width	This events will encounter when page unloads.
Height	This events will encounter when page loads.
Align	This events will encounter when page unloads.
Valign	This events will encounter when page loads.
Bgcolor	This events will encounter when page unloads.
Background	This events will encounter when page loads.

HTML Id Attribute

This is very common attribute of HTML element to distinguish each element from others. In HTML web page, multiple element may have same name but id cannot it must be unique.

Example

//This is correct syntax
<p name="section" id="elementSection1" align="left">Adding content 
of paragraph element.</p>

//This is also correct syntax
<p name="section" id="elementSection2" align="left">Adding content 
of paragraph element.</p>

//This is incorrect syntax id must be unique
<p name="section" id="elementSection1" align="left">Adding content 
of paragraph element.</p>

HTML Alt Attribute

This is very common attribute of HTML element to display brief information about that element. Let's assume that you have web page that content list of "img" element and you want to display some brief information about each image when user mouse over on particular image.

Example

//This is correct syntax
<img src="image.gif" alt="This is image from US."/>

<img src="image.gif" alt="This is image from UK."/>

<img src="image.gif" alt="This is image from INDIA."/>

HTML Width and Height Attribute

This is very common attribute of HTML element to display set width and height for element. Let's assume that you have web page that contains a list of "img" elements and you want to display all images in equal width and height. In HTML, width and height can be set in "px" for example width="100px" or in percentage as width="100%".

Example

<img src="image.gif" alt="This is image from US." width="25px" height="55px"/>

<img src="image.gif" alt="This is image from UK." width="25%" height="55%"/>

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