XHTML和HTML有什么不同？

The Most Important Differences:

XHTML elements must be properly nested（Tag必须严格成对出现）
XHTML elements must always be closed（必须有EndTag,单个Tag必须有/作为结束标记，如:<br/>）
XHTML elements must be in lowercase（必须小写）
XHTML documents must have one root element（只有一个根元素）

XHTML Elements Must Be Properly Nested

In HTML, some elements can be improperly nested within each other, like this:

<b><i>This text is bold and italic</b></i>

In XHTML, all elements must be properly nested within each other, like this:

<b><i>This text is bold and italic</i></b>

Note: A common mistake with nested lists, is to forget that the inside list must be within <li> and </li> tags.

This is wrong:

<ul>

            <li>Coffee</li>

            <li>Tea

            <ul>

            <li>Black tea</li>

            <li>Green tea</li>

            </ul>

            <li>Milk</li>

            </ul>

This is correct:

<ul>

            <li>Coffee</li>

            <li>Tea

            <ul>

            <li>Black tea</li>

            <li>Green tea</li>

            </ul>

            </li>

            <li>Milk</li>

            </ul>

Notice that we have inserted a </li> tag after the </ul> tag in the "correct" code example.

XHTML Elements Must Always Be Closed

Non-empty elements must have an end tag.

This is wrong:

<p>This is a paragraph

            <p>This is another paragraph

This is correct:

<p>This is a paragraph</p>

            <p>This is another paragraph</p>

Empty Elements Must Also Be Closed

Empty elements must either have an end tag or the start tag must end with />.

This is wrong:

A break: <br>

            A horizontal rule: <hr>

            An image: <img src="happy.gif" alt="Happy face">

This is correct:

A break: <br />

            A horizontal rule: <hr />

            An image: <img src="happy.gif" alt="Happy face" />

XHTML Elements Must Be In Lower Case

The XHTML specification defines that the tag names and attributes need to be lower case.

This is wrong:

<BODY>

            <P>This is a paragraph</P>

            </BODY>

This is correct:

<body>

            <p>This is a paragraph</p>

            </body>

XHTML Documents Must Have One Root Element

All XHTML elements must be nested within the <html> root element. All other elements can have sub (children) elements. Sub elements must be in pairs and correctly nested within their parent element. The basic document structure is:

<html>

            <head> ... </head>

            <body> ... </body>

            </html>

posted on 2008-01-10 15:29 Liu Jian 阅读(273) 评论(0) 编辑收藏举报