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HTML文档规范化简洁化 HTML TIDY介绍及使用

[ 来源:W3C | 时间:2008年03月17日 | 收藏本文 ] 【
Layout style

You can choose which style you want Tidy to use when it generates the cleaned up markup: for instance whether you like elements to indent their contents or not. Several people have asked if Tidy could preserve the original layout. I am sorry to say that this would be very hard to support due to the way Tidy is implemented. Tidy starts by building a clean parse tree from the source file. The parse tree doesn't contain any information about the original layout. Tidy then pretty prints the parse tree using the current layout options. Trying to preserve the original layout would interact badly with the repair operations needed to build a clean parse tree and considerably complicate the code.

Some browsers can screw up the right alignment of text depending on how you layout headings. As an example, consider:

<h1 align="right">
  Heading
</h1>
<h1 align="right">Heading</h1>

Both of these should be rendered the same. Sadly a common browser bug fails to trim trailing whitespace and misaligns the first heading. HTML Tidy will protect you from this bug, except when you set the indent option to "yes".

Setting the indent option to yes can also cause problems with table layout for some browsers:

<td><img src="foo.gif"></td>
<td><img src="foo.gif"></td>

will look slightly different from:

<td>
  <img src="foo.gif">
</td>
<td>
  <img src="foo.gif">
</td>

You can avoid such quirks by using indent: no or indent: auto in the config file.

Internationalization issues

Tidy offers you a choice of character encodings: US ASCII, ISO Latin-1, UTF-8 and the ISO 2022 family of 7 bit encodings. The full set of HTML 4.0 entities are defined. Cleaned up output uses HTML entity names for characters when appropriate. Otherwise characters outside the normal range are output as numeric character entities. Tidy defaults to assuming you want the output to be in US ASCII. Tidy doesn't yet recognize the use of the HTML meta element for specifying the character encoding.

Accessibility

Tidy offers advice on accessibility problems for people using non-graphical browsers. The most common thing you will see is the suggestion you add a summary attribute to table elements. The idea is to provide a summary of the table's role and structure suitable for use with aural browsers.

Cleaning up presentational markup

Many tools generate HTML with an excess of FONT, NOBR and CENTER tags. Tidy's -clean option will replace them by style properties and rules using CSS. This makes the markup easier to read and maintain as well as reducing the file size! Tidy is expected to get smarter at this in the future.

Some pages rely on the presentation effects of isolated <p> or </p> tags.Tidy deletes empty paragraph and heading elements etc. The use of empty paragraph elements is not recommended for adding vertical whitespace. Instead use style sheets, or the <br> element. Tidy won't discard paragraphs only containing a nonbreaking space  

Teaching Tidy about new tags!

You can teach Tidy about new tags by declaring them in the configuration file, the syntax is:

  new-inline-tags: tag1, tag2, tag3
  new-empty-tags: tag1, tag2, tag3
  new-blocklevel-tags: tag1, tag2, tag3
  new-pre-tags: tag1, tag2, tag3

The same tag can be defined as empty and as inline or as empty and as block.

These declarations can be combined to define an a new empty inline or empty block element, but you are not advised to declare tags as being both inline and block!

Note that the new tags can only appear where Tidy expects inline or block-level tags respectively. This means you can't (yet) place new tags within the document head or other contexts with restricted content models. So far the most popular use of this feature is to allow Tidy to be applied to Cold Fusion files.

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