HTML 5: Is it , , or ?-第3页回答

I've tried checking other answers, but I'm still confused--especially after seeing W3schools HTML 5 reference.

I thought HTML 4.01 was supposed to "allow" single-tags to just be <img> and  . Then XHTML came along with <img /> and   (where someone said that the space is there for older browsers).

Now I'm wondering how I'm supposed to format my code when practicing HTML 5.

<!DOCTYPE HTML>

Is it  ,   or  ?

标签： html html5

24条回答

ら面具成の殇う

2楼-- · 2018-12-31 04:57

Most of the cases in HTML, the tags are in pair. But for a line break you don't need a pair of tags. Therefore to indicate this, HTML uses   format.   is the right one. Use that format.

  tag has no end tag in HTML In XHTML, the   tag must be properly closed, like this:  

In XML every tag must be closed. XHTML is an extension of XML, hence all the rules of XML must be followed for valid XHTML. Hence even empty tags (nodes without child nodes) like
should be closed. XML has a short form called self closing tags for empty nodes. You can write  as . Hence in XHTML   is used.

HTML is very lenient in this regard, and there is no such rule. So in HTML empty nodes like  <hr> <meta> etc are written without the closing forward slash.

HTML

<br>
<hr>
<meta name="keywords" content="">
<link rel="canonical" href="http://www.google.com/">

XHTML

<br />
<hr />
<meta name="keywords" content="" />
<link rel="canonical" href="http://www.google.com/" />

Not all tags can be self closed. For example, a tag like <script src="jQuery.min.js" /> is not allowed by XHTML DTD.

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谁念西风独自凉

3楼-- · 2018-12-31 04:58

Well all I know is that   gives a break with a white line and   just gives a break in some cases. This happened to me when I was setting up an IPN-script (PHP) and sent mails and checked the inbox for it. Dont know why but I only got the message to look neat using both  and 

Have a look at the mail here: http://snag.gy/cLxUa.jpg

The first two sections of text is seperated by  , hence the whitespace lines, the last three rows of text in the bottom and the last section is seperated by   and just gives new row.

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看风景的人

4楼-- · 2018-12-31 05:02

  works just fine. The stricter versions like XHTML require you to add the closing, and really old versions of HTML that do not include a DOCTYPE make   a non-void tag, like  .

Sum up:   is fine. Other ones are also just fine.

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只靠听说

5楼-- · 2018-12-31 05:04

I would recommend using for the following reasons:

1) Text and XML editors that highlight XML syntax in different colours will highlight properly with but this is not always the case if you use

2) is backwards-compatible with XHTML and well-formed HTML (ie: XHTML) is often easier to validate for errors and debug

3) Some old parsers and some coding specs require the space before the closing slash (ie: instead of ) such as the WordPress Plugin Coding spec: http://make.wordpress.org/core/handbook/coding-standards/html/

I my experience, I have never come across a case where using is problematic, however, there are many cases where or especially might be problematic in older browsers and tools.

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旧时光的记忆

6楼-- · 2018-12-31 05:04

  is sufficient but in XHTML   is preferred according to the WHATWG and according to the W3C.

To quote Section 8.1.2.1 of HTML 5.2 W3C Recommendation, 14 December 2017

Start tags must have the following format:

…

After the attributes, or after the tag name if there are no attributes, there may be one or more space characters. (Some attributes are required to be followed by a space. See §8.1.2.3 Attributes below.)

Then, if the element is one of the void elements, or if the element is a foreign element, then there may be a single U+002F SOLIDUS character (/). This character has no effect on void elements, but on foreign elements it marks the start tag as self-closing.

If you use Dreamweaver CS6, then it will autocomplete as  .

To validate your HTML file on W3C see : http://validator.w3.org/

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萌妹纸的霸气范

7楼-- · 2018-12-31 05:06

XML doesn't allow leaving tags open, so it makes   a bit worse than the other two. The other two are roughly equivalent with the second preferred for compatibility with older browsers. Actually, space before / is preferred for compatibility sake, but I think it only makes sense for tags that have attributes. So I'd say either   or  , whichever pleases your aesthetics.

To sum it up: all three are valid with the first one being a bit less "portable".

Edit: Now that we're all crazy about specs, I think it worth pointing out that according to dev.w3.org:

Start tags consist of the following parts, in exactly the following order:

A "<" character.

The element’s tag name.

Optionally, one or more attributes, each of which must be preceded by one or more space characters.

Optionally, one or more space characters.

Optionally, a "/" character, which may be present only if the element is a void element.

A ">" character.

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HTML 5: Is it , , or ?

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HTML 5: Is it
,
, or
?