对 < head > 中的元素进行排序的最佳实践是什么？

在 <title>之前放置 <meta http-equiv="Content-Type" content="text/html;charset=UTF-8">是重要的吗

这是最常用的，是最好的方法吗？

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">


<html lang="en">


<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>Title Goes Here</title>
<link rel="stylesheet" href="http://sstatic.net/so/all.css?v=5912">
<link rel="shortcut icon" href="http://sstatic.net/so/favicon.ico">
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
<script type="text/javascript">
$(function() {


$("#wmd-input").focus();
$("#title").focus();
$("#revisions-list").change(function() { window.location = '/posts/1987065/edit/' + $(this).val(); });


});
</script>




</head>


<body>
<p>This is my web page</p>


<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/mootools.js"></script>
</body>


</html>

这个站点 http://stackoverflow.com没有任何编码和 <meta>

我使用的 CMS，其中有搜索引擎优化组件，增加了每个 <meta>的搜索引擎优化后，所有的 js 和 css。文件。<head>中允许以任何顺序放置任何元素是否会影响文档的兼容性和编码？

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最佳答案

In HTML, the DOCTYPE must come first, followed by a single <html> element, which must contain a <head> element containing a <title> element, followed by a <body> element. See the description of the global structure of an HTML document in HTML 4.01 and the HTML5 draft; the actual requirements are mostly the same other than the DOCTYPE, but they are described differently.

The actual tags (<html>, </html>, <head>, etc) are optional; the elements will be created automatically if the tags don't exist. <title> is the only required tag in HTML. The shortest valid HTML 4.01 document (at least, that I could generate) is (needs a <p> because there needs to be something in the <body> to be valid):

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd"><title></title><p>

And the shortest valid HTML5 document:

<!DOCTYPE html><title></title>

Note that in XHTML, all tags must be specified explicitly; no elements will be inserted implicitly.

Browsers perform content type sniffing in some circumstances to determine the type of a resource that hasn't been specified using a Content-Type HTTP header, and also character encoding sniffing if the Content-Type header hasn't been supplied or doesn't include a charset (you should generally try to include these headers, and make sure that they are correct, but there are some circumstances in which you cannot, such as local files not transferred over HTTP). They only sniff a limited number of bytes at the beginning of the document for these purposes, though, so anything that is intended to affect the content sniffing or character encoding sniffing should be near the beginning of the document.

For this reason, HTML5 specifies that any meta tag which is used to specify the character set (either <meta http-equiv="Content-type" content="text/html; charset=..."> or simply <meta charset=...>) must be within the first 1024 bytes of the file in order to take effect. So, if you are going to include character encoding information within your document, you should put the tag early in the file, possibly even before the <title> element. But recall that this tag is unnecessary if you properly specify a Content-type header.

In CSS, later style declarations take precedence over earlier ones, all else being equal. So, you should generally put the most generic style sheets that may be overridden earlier, and the more specific style sheets later.

For performance reasons, it can be a good idea to put scripts at the bottom of the page, right before the </body>, because loading scripts blocks the rendering of the page.

Obviously, <script> tags should be ordered so that scripts that depend on each order have the dependencies loaded first.

On the whole, other than the constraints I have already specified, the ordering of tags within <head> shouldn't matter too much, other than for readability. I tend to like to see the <title> towards the top, and put the other <meta> tags in some sort of logical order.

Most of the time, the order you should put things into the body of an HTML document should be the order they should be displayed in, or the order they should be accessed. You can use CSS to rearrange things, but screen readers will generally read things in source order, search indexes will extract things in source order, and so on.

小开

You want your content-type first as this denotes the character encoding, otherwise if it comes later on, some browsers attempt to guess the encoding. (I can't remember the specifics, but I think IE will guess if it doesn't find an encoding in the first 75 characters of the document?)

Most webservers send the encoding in the HTTP headers, but if a user saves your page, the headers aren't saved with it.

I'd put CSS references second so the browser downloads them as soon as possible.

JavaScript I wouldn't put in the head, it should go at the bottom of your pages as downloading them blocks rendering of pages.

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IIRC, some browsers will re-load the document upon encountering a content-type element. So that element should probably come first within the head element of the document.

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Most browsers don't mind how you order your elements, but you should always specify charset first.

Best practices for IE7+ require that the charset, X-UA-Compatible, and base declarations occur before anything else in the head, otherwise the browser starts over and re-parses everything that came before.

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Adding a few performance suggestions to Brian's answer, highest priority should logically be things that will need to be downloaded, so the browser can start downloading them asap, and things that will affect how the page is presented. So I'd suggest:

  • Metas affecting appearance, such as charset (required early by the spec too), viewport, apple-mobile-web-app-capable
  • Title near the top so the browser can render it asap and user has a sense something is happening
  • Favicon and touch icons
  • CSS (at least CSS for above-the-fold; other CSS can be loaded in the footer if you want to get fancy). This step typically blocks everything else from proceeding, which is why I put the previous items above it, as they provide some feedback during the CSS delay.
  • Critical scripts (such as user-agent sniffing that may affect layout) which can't be loaded in the footer
  • Everything else (e.g. necessary metadata in the form of links and meta tags)

You might also consider inlining whatever CSS and JS is loaded in head, especially if its small and the external script/sheet is unlikely to be cached according to your typical visitor's profile. And if you do inline it, you'll ideally want to compress it.

Last thing: The user has to wait around for head - and any blocking resources it loads - so it's best to put as much as possible in the body or footer.

小开

According to W3 should be:

  • Meta charset
  • Title
  • Meta name="descripition"
  • Meta name="keywords"
  • Stylesheet
  • JavaScript Files
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This is the template I use, just delete whatever you dont need for a new project.

<!doctype html>
<html class="no-js" lang="en">
<head>
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />


<title></title>


<meta name="description" content="">
<meta name="keywords" content="">
<meta name="author" content="">


<meta name="robots" content="index, follow">
<meta name="mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="default">


<link rel="stylesheet" href="scss/style.css" />


<!-- http://realfavicongenerator.net/ -->


<meta property="fb:page_id" content="">
<meta property="og:title" content="">
<meta property="og:image" content="">
<meta property="og:description" content="">
<meta property="og:url" content="">
<meta property="og:site_name" content="">
<meta property="og:type" content="website">


<meta name="twitter:card" content="summary">
<meta name="twitter:url" content="">
<meta name="twitter:title" content="">
<meta name="twitter:description" content="">
<meta name="twitter:image" content="">
<meta name="twitter:site" content="">


<script src="js/vendor/modernizr.js"></script>
</head>
<body>
</body>
</html>

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