Attributes provide additional information about HTML elements.
An HTML attribute is a modifier of an HTML element type. An attribute either modifies the default functionality of an element type or provides functionality to certain element types unable to function correctly without them. In HTML syntax, an attribute is added to an HTML start tag.
HTML Attributes
- HTML elements can have attributes
- Attributes provide additional information about an element
- Attributes are always specified in the start tag
- Attributes come in name/value pairs like: name="value"
Description
HTML attributes generally appear as name-value pairs, separated by =, and are written within the start tag of an element, after the element's name:
<tag attribute="value">content to be modified by the tag</tag>
Where tag names the HTML element type, and attribute is the name of the attribute, set to the provided value. The value may be enclosed in single or double quotes, although values consisting of certain characters can be left unquoted in HTML (but not XHTML).Leaving attribute values unquoted is considered unsafe.
Although most attributes are provided as paired names and values, some affect the element simply by their presence in the start tag of the element (like the ismap attribute for the img element).
Most elements can take any of several common attributes:
The id attribute provides a document-wide unique identifier for an element.This can be used as CSS selector to provide presentational properties, by browsers to focus attention on the specific element, or by scripts to alter the contents or presentation of an element. Appended to the URL of the page, the URL directly targets the specific element within the document, typically a sub-section of the page. For example, the ID "Attributes".
The class attribute provides a way of classifying similar elements. This can be used for semantic purposes, or for presentation purposes. Semantically, for example, classes are used in microformats. Presentationally, for example, an HTML document might use the designation class="notation" to indicate that all elements with this class value are subordinate to the main text of the document. Such elements might be gathered together and presented as footnotes on a page instead of appearing in the place where they occur in the HTML source. Another presentation use would be as a CSS selector.
An author may use the style non-attributal codes presentational properties to a particular element. It is considered better practice to use an element's id or class attributes to select the element with a stylesheet, though sometimes this can be too cumbersome for a simple and specific or ad hoc application of styled properties.
The title attribute is used to attach subtextual explanation to an element. In most browsers this attribute is displayed as what is often referred to as a tooltip.
The abbreviation element, abbr, can be used to demonstrate these various attributes:
<abbr id="anId" class="aClass" style="color:blue;" title="Hypertext Markup Language">HTML</abbr>
This example displays as HTML; in most browsers, pointing the cursor at the abbreviation should display the title text "Hypertext Markup Language."
Most elements also take the language-related attributes lang and dir.
The lang Attribute
The document language can be declared in the <html> tag.
The language is declared in the lang attribute.
Declaring a language is important for accessibility applications (screen readers) and search engines:
<!DOCTYPE html>
<html lang="en-US">
<body>
<h1>My First Heading</h1>
<p>My first paragraph.</p>
</body>
</html>
The first two letters specify the language (en). If there is a dialect, use two more letters (US).
The title Attribute
HTML paragraphs are defined with the <p> tag.
In this example, the <p> element has a title attribute. The value of the attribute is "About w3im":
Example
<p title="About w3ii">
w3ii is a web developer's site.
It provides tutorials and references covering
many aspects of web programming,
including HTML, CSS, JavaScript, XML, SQL, PHP, ASP, etc.
</p>
Try it Yourself »When you move the mouse over the element, the title will be displayed as a tooltip.
The href Attribute
HTML links are defined with the <a> tag. The link address is specified in the href attribute:
You will learn more about links and the <a> tag later in this tutorial.
Size Attributes
HTML images are defined with the <img> tag.
The filename of the source (src), and the size of the image (width and height) are all provided as attributes:
The image size is specified in pixels: width="104" means 104 screen pixels wide.
You will learn more about images and the <img> tag later in this tutorial.
The alt Attribute
The alt attribute specifies an alternative text to be used, when an HTML element cannot be displayed.
The value of the attribute can be read by "screen readers". This way, someone "listening" to the webpage, i.e. a blind person, can "hear" the element.
We Suggest: Always Use Lowercase Attributes
The HTML5 standard does not require lower case attribute names.
The title attribute can be written with upper or lower case like Title and/or TITLE.
W3C recommends lowercase in HTML4, and demands lowercase for stricter document types like XHTML.
Lower case is the most common. Lower case is easier to type.
At w3ii we always use lower case attribute names.
We Suggest: Always Quote Attribute Values
The HTML5 standard does not require quotes around attribute values.
The href attribute, demonstrated above, can be written as:
W3C recommends quotes in HTML4, and demands quotes for stricter document types like XHTML.
Sometimes it is necessary to use quotes. This will not display correctly, because it contains a space:
Using quotes are the most common. Omitting quotes can produce errors.
At w3ii we always use quotes around attribute values.
Single or Double Quotes?
Double style quotes are the most common in HTML, but single style can also be used.
In some situations, when the attribute value itself contains double quotes, it is necessary to use single quotes:
<p title='John "ShotGun" Nelson'>
Or vice versa:
<p title="John 'ShotGun' Nelson">
Chapter Summary
- All HTML elements can have attributes
- The HTML title attribute provides additional "tool-tip" information
- The HTML href attribute provides address information for links
- The HTML width and height attributes provide size information for images
- The HTML alt attribute provides text for screen readers
- At w3ii we always use lowercase HTML attribute names
- At w3ii we always quote attributes with double quotes
Test Yourself with Exercises!
Exercise 1 » Exercise 2 » Exercise 3 » Exercise 4 » Exercise 5 »
HTML Attributes
Below is an alphabetical list of some attributes often used in HTML:
| Attribute | Description |
|---|---|
| alt | Specifies an alternative text for an image |
| disabled | Specifies that an input element should be disabled |
| href | Specifies the URL (web address) for a link |
| id | Specifies a unique id for an element |
| src | Specifies the URL (web address) for an image |
| style | Specifies an inline CSS style for an element |
| title | Specifies extra information about an element (displayed as a tool tip) |
A complete list of all attributes for each HTML element, is listed in our: HTML Tag Reference.