Span and div

In HTML, the span and div elements are used for generic organizational or stylistic applications, typically when extant meaningful elements have exhausted their purpose.

Most HTML elements signify the specific meaning of their content – i.e. the element describes, and can be made to function according to, the type of data contained within. For example, a p element should contain a paragraph of text, while an h1 element should contain the highest-level heading of the page or section^[1]; user agents should distinguish them accordingly. span and div signify no specific meaning besides the generic grouping of content, and are therefore more appropriate for creating organization or stylistic additions without signifying superfluous meaning.

History

The code tag were introduced to HTML in the internationalization WG second draft html-i18n on 1995-09-25. However it was not until HTML 4.01 the new element became part of the HTML language and appeared in the HTML 4 W3C Working Draft on 1997-09-17.^[2]

Differences and default behavior

There are multiple differences between div and span. The most notable difference is how the elements are displayed. In standard HTML, a div is a block-level element whereas a span is an inline element. The div block visually isolates a section of a document on the page, and may contain other block-level components. The span element contains a piece of information inline with the surrounding content, and may only contain other inline-level components. In practice, the default display of the elements can be changed by the use of Cascading Style Sheets (CSS), however the permitted contents of each element may not be changed. For example, regardless of CSS, a span element may not contain block-level children.^[3]

Practical usage

span and div elements are used purely to imply a logical grouping of enclosed elements.

There are three main reasons to use span and div tags with class or id attributes:

Styling with CSS

Perhaps the most common use of <span> and <div> elements is to carry class or id attributes in conjunction with CSS to apply layout, typographic, color, and other presentation attributes to parts of the content. CSS does not just apply to visual styling: when spoken out loud by a voice browser, CSS styling can affect speech-rate, stress, richness and even position within a stereophonic image.

For these reasons, and for compatibility with the concepts of the semantic web, discussed below, attributes attached to elements within any HTML should describe their semantic purpose, rather than merely their intended display properties in one particular medium. For example, the HTML in <span class="red-bold">password too short</span> is semantically weak, whereas <em class="warning">password too short</em> uses an em element to signify emphasis, and uses a more appropriate class name. By the correct use of CSS, 'warnings' may be rendered in a red, bold font on a screen, but when printed out they may be omitted, as by then it is too late to do anything about them. Perhaps when spoken they should be given extra stress, and a small reduction in speech-rate. The second example is semantically correct markup, rather than merely presentational.

Semantic clarity

This kind of grouping and labeling of parts of the page content might be introduced purely to make the page more semantically meaningful in general terms. It is impossible to say how and in what ways the World Wide Web will develop in years and decades to come. Web pages designed today may still be in use when information systems that we cannot yet imagine are trawling, processing, and classifying the web. Even today's search engines such as Google and others use proprietary information processing algorithms of considerable complexity.

For some years, the World Wide Web Consortium (W3C) has been running a major Semantic Web project designed to make the whole web increasingly useful and meaningful to today's and the future's information systems.

The microformats movement is an attempt to build an idea of semantic classes. For example, microformats-aware software might automatically find an element like <span class="tel">123-456-7890</span> and allow for automatic dialing of the telephone number.

Access from code

Once the HTML or XHTML markup is delivered to a page-visitor's client browser, there is a chance that client-side code will need to navigate the internal structure (or Document Object Model) of the web page. The most common reason for this is that the page is delivered with client-side JavaScript that will produce on-going dynamic behavior after the page is rendered. For example, if rolling the mouse over a 'Buy now' link is meant to make the price, elsewhere on the page, become emphasized, JavaScript code can do this, but JavaScript needs to identify the price element, wherever it is in the markup, in order to affect it. The following markup would suffice: <div id="price">$45.99</div>. Another example is the Ajax programming technique, where, for example, clicking a hypertext link may cause JavaScript code to retrieve the text for a new price quotation to display in place of the current one within the page, without re-loading the whole page. When the new text arrives back from the server, the JavaScript must identify the exact region on the page to replace with the new information.

Less common, but just as important examples of code gaining access to final web pages, and having to use span and div elements' class or id attributes to navigate within the page include the use of automatic testing tools. On dynamically generated HTML, this may include the use of automatic page testing tools such as HttpUnit, a member of the xUnit family, and load or stress testing tools such as Apache JMeter when applied to form-driven web sites.

Overuse

The judicious use of div and span is a vital part of HTML and XHTML markup. However, they are sometimes overused.

For example, when structurally and semantically a series of items need an outer, containing element and then further containers for each item, then there are various list structures available in HTML, one of which may be preferable to a homemade mixture of div and span elements.^[4]

For example, this...

<ul class="menu">
  <li>Main page</li>
  <li>Contents</li>
  <li>Help</li>
</ul>

...is usually preferable to this:

<div class="menu">
  <span>Main page</span>
  <span>Contents</span>
  <span>Help</span>
</div>

Other examples of the semantic use of HTML rather than div and span elements include the use of fieldset elements to divide up a web form, the use of legend elements to identify such divisions and the use of label to identify form input elements rather than div, span or table elements used for such purposes.^[5]

HTML5 introduces new elements; a few examples include the header, footer, nav and figure elements.^[6]

See also

• HTML
• HTML element
• HTML attribute
• Cascading Style Sheets
• CDATA
• JavaScript
• Semantic Web

References

External links

• Grouping elements: the DIV and SPAN elements
• Create Horizontal and Vertical Aligned DIV