Best HTML5 markup for sidebar - html

I'm setting up my WordPress sidebars for an HTML5 theme and really wanting to use before_widget and after_widget right.
So my question is this: which of the two markup patterns is more appropriate? The following code is all completely outside the <article> element.
Option 1: Aside with sections
<aside id="sidebar">
<section id="widget_1"></section>
<section id="widget_2"></section>
<section id="widget_3"></section>
</aside>
Option 2: Div with Asides
<div id="sidebar">
<aside id="widget_1"></aside>
<aside id="widget_1"></aside >
<aside id="widget_1"></aside >
</div>
I suppose the auxiliary question is then what heading to use for each widget title. If I wrap each widget in a <section> then <h1> seems most appropriate. If I use <aside>, I'm not sure.
All opinions welcome. Devil's advocates encouraged.

First of all ASIDE is to be used only to denote related content to main content, not for a generic sidebar. Second, one aside for each sidebar only
You will have only one aside for each sidebar. Elements of a sidebar are divs or sections inside a aside.
I would go with Option 1: Aside with sections
<aside id="sidebar">
<section id="widget_1"></section>
<section id="widget_2"></section>
<section id="widget_3"></section>
</aside>
Here is the spec https://developer.mozilla.org/en-US/docs/Web/HTML/Element/aside
Again use section only if they have a header or footer in them, otherwise use a plain div.

Update 17/07/27: As this is the most-voted answer, I should update this to include current information locally (with links to the references).
From the spec [1]:
The aside element represents a section of a page that consists of
content that is tangentially related to the content of the parenting
sectioning content, and which could be considered separate from that
content. Such sections are often represented as sidebars in printed
typography.
Great! Exactly what we're looking for. In addition, it is best to check on <section> as well.
The section element represents a generic section of a document or
application. A section, in this context, is a thematic grouping of
content. Each section should be identified, typically by including a
heading (h1-h6 element) as a child of the section element.
...
A general rule is that the section element is appropriate only if the element’s contents would be listed explicitly in the document’s outline.
Excellent. Just what we're looking for. As opposed to <article> [2] which is for "self-contained" content, <section> allows for related content that isn't stand-alone, or generic enough for a <div> element.
As such, the spec seems to suggest that using Option 1, <aside> with <section> children is best practice.
References
https://www.w3.org/TR/html51/sections.html#the-aside-element
https://www.w3.org/TR/html51/sections.html#elementdef-article
http://html5doctor.com/aside-revisited/

Look at the following example, from the HTML5 specification about aside.
It makes clear that what currently is recommended (October 2012) it is to group widgets inside aside elements. Then, each widget is whatever best represents it, a nav, a serie of blockquotes, etc
The following extract shows how aside can be used for blogrolls and
other side content on a blog:
<body>
<header>
<h1>My wonderful blog</h1>
<p>My tagline</p>
</header>
<aside>
<!-- this aside contains two sections that are tangentially related
to the page, namely, links to other blogs, and links to blog posts
from this blog -->
<nav>
<h1>My blogroll</h1>
<ul>
<li>Example Blog
</ul>
</nav>
<nav>
<h1>Archives</h1>
<ol reversed>
<li>My last post
<li>My first post
</ol>
</nav>
</aside>
<aside>
<!-- this aside is tangentially related to the page also, it
contains twitter messages from the blog author -->
<h1>Twitter Feed</h1>
<blockquote cite="http://twitter.example.net/t31351234">
I'm on vacation, writing my blog.
</blockquote>
<blockquote cite="http://twitter.example.net/t31219752">
I'm going to go on vacation soon.
</blockquote>
</aside>
<article>
<!-- this is a blog post -->
<h1>My last post</h1>
<p>This is my last post.</p>
<footer>
<p><a href="/last-post" rel=bookmark>Permalink</a>
</footer>
</article>
<article>
<!-- this is also a blog post -->
<h1>My first post</h1>
<p>This is my first post.</p>
<aside>
<!-- this aside is about the blog post, since it's inside the
<article> element; it would be wrong, for instance, to put the
blogroll here, since the blogroll isn't really related to this post
specifically, only to the page as a whole -->
<h1>Posting</h1>
<p>While I'm thinking about it, I wanted to say something about
posting. Posting is fun!</p>
</aside>
<footer>
<p><a href="/first-post" rel=bookmark>Permalink</a>
</footer>
</article>
<footer>
<nav>
Archives —
About me —
Copyright
</nav>
</footer>
</body>

Based on this HTML5 Doctor diagram, I'm thinking this may be the best markup:
<aside class="sidebar">
<article id="widget_1" class="widget">...</article>
<article id="widget_2" class="widget">...</article>
<article id="widget_3" class="widget">...</article>
</aside> <!-- end .sidebar -->
I think it's clear that <aside> is the appropriate element as long as it's outside the main <article> element.
Now, I'm thinking that <article> is also appropriate for each widget in the aside. In the words of the W3C:
The article element represents a self-contained composition in a
document, page, application, or site and that is, in principle,
independently distributable or reusable, e.g. in syndication. This
could be a forum post, a magazine or newspaper article, a blog entry,
a user-submitted comment, an interactive widget or gadget, or any
other independent item of content.

The book HTML5 Guidelines for Web Developers: Structure and Semantics for Documents suggested this way (option 1):
<aside id="sidebar">
<section id="widget_1"></section>
<section id="widget_2"></section>
<section id="widget_3"></section>
</aside>
It also points out that you can use sections in the footer. So section can be used outside of the actual page content.

I'm surprised that none of the responses above consider responsive design.
I may have valid aside elements such as a tag cloud, links for further reading and so on together, one after the other, in my sidebar when my page is viewed on a desktop device.
However, when my page is reduced on a mobile device to a single column then I will be separating those elements. My navigation element will go between my header and main content elements, and links for further reading will go below the main content element, above the footer.
As the semantic content of these elements is not changing with the width of the display window, then they need to be individually marked up as aside elements.
It follows then, that the sidebar itself should not be marked up as an aside element, even when it only contains content of one type.
In turn, this means that Option 1 in the original question must be undesirable (wrong?) and that the better answer should be Option 2.

The ASIDE has since been modified to include secondary content as well.
HTML5 Doctor has a great writeup on it here:
http://html5doctor.com/aside-revisited/
Excerpt:
With the new definition of aside, it’s crucial to remain aware of its context. >When used within an article element, the contents should be specifically related >to that article (e.g., a glossary). When used outside of an article element, the >contents should be related to the site (e.g., a blogroll, groups of additional >navigation, and even advertising if that content is related to the page).

Related

In html5 can you have an <h1> in a footer

I've looked all over and have yet to find anything that specifically answers this question: In html5 is it semantically ok to have an h1 tag inside of a footer? I know that you can have multiple h1s in a document now but I'm working on a project that involves a footer with a heading and there's some debate going on as to whether or not that is semantic.
There is nothing mutually exclusive about footer and h1 tags. In fact, you can even have multiple footers, too.
Take a look at W3C HTML standard last code example for footer: it contains h1 inside of one:
Some site designs have what is sometimes referred to as "fat footers"
— footers that contain a lot of material, including images, links to
other articles, links to pages for sending feedback, special offers...
in some ways, a whole "front page" in the footer.
This fragment shows the bottom of a page on a site with a "fat
footer":
...
<footer>
<nav>
<section>
<h1>Articles</h1>
...
Semantically this would be very bad as H1 are for representing a header for a section or whatever. Image this for a blind user. There is a discussion on this here:
http://moz.com/community/q/h1-tag-in-the-footer
It should be noted that in your example and link it the h1 in the footer is always wrapped inside a <section></section> tag.
<section> can have its own blocks of self contained content as well
<header>
<!-- nav/logo/etc -->
</header>
<main>
<!-- article/content/section/etc -->
</main>
<footer>
<!-- nav/links/section/etc... -->
<section>
<h1></h1> <!-- h1 in a NEW section -->
</section>
</footer>

<main> inside <article> in HTML5

Plot: When building a coupons website I realize that their can be content that is not unique to the page but should be used inside the <main><article> ..here..</article></main>.
Problem: Just because w3schools state :
The content inside the element should be unique to the
document. It should not contain any content that is repeated across
documents.
But i have content which will be inside article. Like every time for example A coupon can be used by entering its code but a deal can only be activated by going to landing page.
This will be repeated in every 'coupon' post I will publish.
So now what I tried to use was.
<main><article><main>Unique content</main>
<aside>A coupon can be used by entering its code but a deal can only be activated by going to landing page</aside></article></main>
But again :
Note: There must not be more than one <main> element in a document.
The <main> element must NOT be a descendent of an <article>, <aside>,
<footer>, <header>, or <nav> element.
So what is the best way to format the UN-UNIQUE content inside <main> and/or <article>.
The main tag should be used to group those article and aside elements.
<main>
<article>
The unique document content.
</article>
<aside>
Related content for that document.
</aside>
</main>
tl;dr - use your common sense :)
This article on the actual w3 site has a good overview of what should go where. The overall structure is:
<body>
<header>
<!-- header content goes in here -->
</header>
<nav>
<!-- navigation menu goes in here -->
</nav>
<section id="sidebar1">
<!-- sidebar content goes in here -->
</section>
<main>
<!-- main page content goes in here -->
</main>
<aside>
<!-- aside content goes in here -->
</aside>
<footer>
<!-- footer content goes in here -->
</footer>
</body>
Option 1 - <section>s
They go on to say that <section>s, fairly obviously, can contain multiple <articles>, but that it is also possible to put <section>s inside an <article>, for example to define the introduction or summary:
<article>
<section id="introduction">
</section>
<section id="content">
</section>
<section id="summary">
</section>
</article>
So one option is to put a <section id="content"> and <section id="terms"> inside your article.
Option 2 - <footer>s
It does appear valid to use a <footer> for this sort of content. You said it is just for author, date, category, but w3 states in its spec for <footer>:
A footer typically contains information about its section such as who wrote it, links to related documents, copyright data, and the like.
Your text is terms and conditions of a coupon, which could be considered as semantically similar to copyright data. It's a judgement call I think.
Option 3 - <div>s et al...
As a get-out, in the first link they do also say about <div>s:
You should use [a div] when there is no other more suitable element available for grouping an area of content...
So if it really isn't clear what to use, another possibility could be:
<article>
Blah blah
<div class="terms"></div>
</article>
Summary
To be honest, after all this, it seems there is no definitive answer and sites are unlikely to become super-strict in how they semantically parse documents for a while yet, because they know there are legions of people out there who will do it completely wrong. If you just stick a <p> with the same terms in at the end of each article, it probably won't make any real difference because the main text is unique.
I personally think as long as you use your common sense and choose something which doesn't completely go against the recommendations, you can't go too wrong.
According to the WHATWG (the informal group behind the HTML Living Document Standard), there is no problem in using a main element inside an article. The HTML Living Document says:
There is no restriction as to the number of main elements in a document. Indeed, there are many cases where it would make sense to have multiple main elements. For example, a page with multiple article elements might need to indicate the dominant contents of each such element.
Consequently, you can write
<body>
<header>My Page Header</header>
<main>
<article><h1>My First Article</h1>
<main>My first article's content...</main>
<aside>A sidebar</aside>
</article>
<article><h1>My Second Article</h1>
<main>My second article's content...</main>
<aside>Another sidebar</aside>
</article>
</main>
</body>
However, the W3C HTML 5.3 Draft disallows this and states that "There must not be more than one visible main element in a document."
This is an interesting case of a disagreement about a central element of HTML. Amazing! It seems that there is again a schism between W3C authors and the web/browser developer professionals behind the WHATWG. In such a case, I would go with the WHATWG.
I would go with something like this :
<main>
<div class='article'>
<article>Unique content</article>
<footer>This coupon can be used only once..</footer>
</div>
<div class='article'>
<article>Unique content</article>
<footer>This coupon can be used only once..</footer>
</div>
</main>
Anyway I think having multiple <main> tags is worse than having non-unique content in an <article> tag.
You can also take into consideration Schema.org for proper mapping your content with additional attributes ( itemprop ... )

Single HTML aside or multiple asides?

I have some HTML which looks like this
<main>
<article></article>
<aside>
// a widget to show top reasons to shop with us
// a widget to show some related articles
<aside>
</main>
My question is, should each of the widget be contained in their own ASIDE, or should they each be inside a SECTION within the ASIDE or is the current structure OK?
I think that is really up to you and how you wish to style the page. The html specification does not specify a limit on the number aside elements and even gives an example that has multiple aside elements on the same page.
I would say given that they are logically grouped it would make sense to put them together in the same aside element.
http://www.w3.org/TR/html5/sections.html#the-aside-element
The aside container can be use more than one.
html5 uses the type of tag to determine the content over others.
for example if you make this :
<article>
<header>
<h1>your title</h1>
</header>
<p>
your first paragraph
</p>
<p>
your second paragraph
</p>
<aside>
<ul>
<li>ref1</li>
<li>ref2</li>
</ul>
</aside>
</article>
<aside>
more information about you
</aside>
with that you have one aside you is linked with your article and one with the top container (I don't wrote it here)
in the html5 specification, the aside is some content aside from the content then you can define content aside for some other content who is already an
source : http://www.w3.org/html/wg/drafts/html/master/sections.html#the-aside-element

HTML5 section tag meanings?

I know there are tons of questions about this topic but I can't find an authoritative source for the answer.
This is the official definition and the wiki page, and there there is more documentation, but there they don't explain the correct usage if not in a very simple examples or in different ways.
What I've "understood" so far:
<section> defines a part(section) of the page, like blogrolls, headlines news, blog entries list, comments list, and everything which can be with a common topic.
<article> defines a content which has sense estranged from the rest of the page (?) and which has a single topic (blog entry, comment, article, etc).
But, inside an <article>, we can split parts of it in sections using <section>, and in this case it has the function of container to mark chapters of a bigger text.
The doubt
If these sentences are correct (or partially correct) that means that <section> has two completly different usage cases.
We could have a page written in this way:
<!DOCTYPE html>
<html lang=en>
<head>
<meta charset=utf-8>
<title>Fruits</title>
</head>
<body>
<h1>Fruits war blog</h1>
<section id="headlineNews"> <!-- USED AS CONTAINER -->
<h1>What's new about fruits?</h1>
<article><h1>Apples are the best</h1>Apples are better than bananas</article>
<article><h1>Apple's cakes</h1>With apples you can prepare a cake</article>
</section>
<section id="blogEntries"> <!-- USED AS CONTAINER -->
<h1>Articles about fruits</h1>
<article>
<h1>Apples vs Bananas</h1>
<section> <!-- USED AS CHAPTER -->
<h2>Introduction:</h2>
Bananas have always leaded the world but...
</section>
<section> <!-- USED AS CHAPTER -->
<h2>The question:</h2>
Who is the best? We don't know so much about apples...
</section>
</article>
</section>
</body>
</html>
And this is how looks the Outline:
1. Fruits war blog
1. What's new about fruits?
1. Apples are the best
2. Apple's cakes
2. Articles about fruits
1. Apples vs Bananas
1. Introduction:
2. The question:
So the <section> is thought with two completly different and not related semantic meanings?
Is it correct use:
<!-- MY DOUBT -->
<section> <!-- USED AS CONTAINER -->
<article>
<section></section> <!-- USED AS CHAPTER -->
</article>
</section>
in this neasted way?
I've found that is possible to use in the inversed way:
<!-- FROM W3C -->
<article> <!-- BLOG ENTRY -->
<section> <!-- USED AS CHAPTER ABOUT COMMENTS -->
<article></article> <!-- COMMENT -->
</section>
</article>
But I can't find an answer to the way I've written below.
I guess read the discussion where the W3C group has wrote the basis of the <section> tag could be useful but I can't find it.
N.B. I'm looking for replies documented with authorative sources
http://www.w3.org/wiki/HTML/Elements/section is not the official definition of section. section is defined in the HTML5 specification, which currently is a Candidate Recommendation (which is a snapshot of the Editor’s Draft).
In the CR, section is defined as:
The section element represents a generic section of a document or application. A section, in this context, is a thematic grouping of content, typically with a heading.
section is a sectioning content element (together with article, aside and nav). Those sectioning elements and the headings (h1-h6) create an outline.
The following three examples are semantically equivalent (same meaning, same outline):
<!-- example 1: using headings only -->
<h1>My first day</h1>
<p>…</p>
<h2>Waking up</h2>
<p>…</p>
<h2>The big moment!</h2>
<p>…</p>
<h2>Going to bed</h2>
<p>…</p>
<!-- example 1: using section elements with corresponding heading levels -->
<section>
<h1>My first day</h1>
<p>…</p>
<section>
<h2>Waking up</h2>
<p>…</p>
</section>
<section>
<h2>The big moment!</h2>
<p>…</p>
</section>
<section>
<h2>Going to bed</h2>
<p>…</p>
</section>
</section>
<!-- example 1: using section elements with h1 everywhere -->
<section>
<h1>My first day</h1>
<p>…</p>
<section>
<h1>Waking up</h1>
<p>…</p>
</section>
<section>
<h1>The big moment!</h1>
<p>…</p>
</section>
<section>
<h1>Going to bed</h1>
<p>…</p>
</section>
</section>
So you can use section whenever (*) you use h1-h6. And you use section when you need a separate entry in the outline but can’t (or don’t want to) use a heading.
Also note that header and footer always belong to its nearest ancestor sectioning content (or sectioning root, like body, if there is no sectioning element) element. In other words: each section/article/aside/nav element can have its own header/footer.
article, aside and nav are, so to say, more specific variants of the section element.
two completly different usage cases
These two use-cases are not that different at all. In the "container" case, you could say that section represents a chapter of the document, while in the "chapter" case section represents a chapter of the article/content (which, ouf course, is part of the document).
In the same way, some headings are used to title web page parts (like "Navigation", "User menu", "Comments", etc.), and some headings are used to title content ("My first day", "My favorite books", etc.).
<article> and <section> are both sectioning content. You can nest one sectioning element inside another to slice up the outer element into sections.
HTML Living Standard, 4.4.11:
...
Sectioning content elements are always considered subsections of their nearest ancestor sectioning root or their nearest ancestor element of sectioning content, whichever is nearest, regardless of what implied sections other headings may have created.
...
You can consider a <section> as a generic sectioning element. It's like a <div> that defines a section within its closest sectioning parent (or the nearest sectioning root, which may be the <body>).
An <article> is also a section, but it does have some semantics. Namely, it represents content that is self-contained (that is, it could possibly be its own page and it'd still make sense).
OK so here is what I've gathered from authorative sources.
MDN:
The HTML Section Element () represents a generic section of a document, i.e., a thematic grouping of content, typically with a heading.
Usage notes :
If it makes sense to separately syndicate the content of a element, use an element instead.
Do not use the element as a generic container; this is what is for, especially when the sectioning is only for styling purposes. A rule of thumb is that a section should logically appear in the outline of a document.
Shay Howe's guide:
A section is more likely to get confused with a div than an article. As a block level element, section is defined to represent a generic document or application section.
The best way to determine when to use a section versus a div is to look at the actual content at hand. If the block of content could exist as a record within a database and isn’t explicitly needed as a CSS styling hook then the section element is most applicable. Sections should be used to break a page up, providing a natural hierarchy, and most commonly will have a proper heading.
dev.opera.com
Basically, the article element is for standalone pieces of content that would make sense outside the context of the current page, and could be syndicated nicely. Such pieces of content include blog posts, a video and it's transcript, a news story, or a single part of a serial story.
The section element, on the other hand is for breaking the content of a page into different functions or subjects areas, or breaking an article or story up into different sections.
Here's the official w3c take on section:
http://www.w3.org/wiki/HTML/Elements/section
Quote: "The [section] element represents a generic section of a document or application."
I guess, in theory if you have an article within an article then your nested selections example might work. But, why would you have an article within an article ? Makes little semantic sense.

Nesting HTML5 section tags

Is this a correct way to use the <section> tag?
<section id="container">
<section id="outer">
<section id="inner">
</section>
</section>
</section>
I'm trying to work out whether or not I should use only one section id, and leave the other two sections as just divs?
If you are just using these elements to place things in some position / style things, then you should probably be using divs.
Section is really for grouping content that belongs together - you shouldn't really have a section without a title (H1 or similar) element describing what the section contains... a few people have made similar mistakes in the past I think:
http://html5doctor.com/the-section-element/
From the spec:
NOTE: The section element is not a generic container element. When an
element is needed for styling purposes or as a convenience for
scripting, authors are encouraged to use the div element instead. A
general rule is that the section element is appropriate only if the
element's contents would be listed explicitly in the document's
outline.
Having said that, it's perfectly acceptable to nest section elements. Maybe something like:
<section>
<h1>Portishead</h1>
<p>Portishead are a cool band from Bristol</p>
<section>
<h1>Dummy (album)</h1>
<p>some info....</p>
<img src="..." />
</section>
<section>
<h1>Portishead (album)</h1>
<p>some other info info....</p>
<img src="..." />
</section>
</section>
Note:
My answer is severely out-of-date, and no longer contains sound advice given the changes to HTML that have happened in the last decade. I will be leaving this answer as-is for historical context, but please be aware that the structure suggested is not best practice—particularly around the use of the obsolete document outline.
Short answer: The code as you've provided is not semantically valid.
Long answer:
section elements are meant to mark up sections of content. Each section of content (i.e. Introduction, Abstract, content, conclusion) could have subsections.
If you're using those elements for structural purpose, you should be using div elements instead. They are semantically meaningless.
This would be more semantic:
<section id="introduction">
<div id="outer">
<div id="inner">
Some content
</div>
</div>
</section>
This would be a semantic way of marking up nested sections:
<section id="content">
<h1>Fizz Buzz</h1>
<section id="chapter-1">
<h1>Foo bar baz</h1>
...
</section>
<section id="chapter-2">
<h1>Lorem ipsum dolor</h1>
...
</section>
....
</section>
My personal recommendation would be to utilize semantic structure as much as possible when you create HTML5 layouts. As other posters have indicated, nesting section elements is totally acceptable, however you need to just make sure it makes sense to do so.
I personally use a few patterns that I've put together based on some research I've done over the course of the last year or so. The most common situation for using nested section elements is to provide ARIA roles for the main content of the document (see "site layout" example below)
Note: assumes body/html elements are present, etc
Site Layout
<header class="header" role="banner">
....
</header>
<!-- used once per page, implies role="main" -->
<main>
<!-- declares page content to be a document and not a web app -->
<section id="wrapper" role="document">
<section class="hero">
....
</section>
....
<section class="content">
</section>
</section>
</main>
<footer class="footer" role="footer">
....
</footer>
Single-Page Content Layout
Note: This layout applies to a page with a singular/topic/object and isn't suitable for all use cases
<article>
<header>
<h1>Page Headline/Title</h1>
</header>
<section class="page-content">
....
</section>
<!-- if this is a post or something with metadata/authorship info... -->
<footer>
....
</footer>
</article>
I use the tag for the class name on the shell header/footer elements as well as landmark roles to insure I can always distinguish them from other header/footer elements within the page (e.g. easy CSS scoping).
References
role="document" https://www.w3.org/TR/wai-aria/roles#document
A region containing related information that is declared as document content, as opposed to a web application.
"Why the <main> element doesn't need a role attribute": https://www.w3.org/TR/2012/WD-html-main-element-20121217/
The main element formalises the common practice of identification of the main content section of a document using the id values such as 'content' and 'main'. It also defines an HTML element that embodies the semantics and function of the WAI-ARIA landmark role=main.
"W3.org/Wiki explanation of nesting <section> elements" - https://www.w3.org/WAI/GL/wiki/Using_HTML5_section_element
The section element is a container for document content that has a related theme, and represents the section of a document that is grouped around a general concept. Everything within a section element is related. Also section elements may be nested if necessary. The section element is a generic semantic element, that can be used to combine portions of a document together into discrete units that are related in some way. For example, the section element may create items inside an outline of a document, or divide page content into related pieces (like an Introduction) followed by some background information on the topic.
A useful way to think through this is to consider how a screen reader would see your site. Imagine (and in fact you should test this for yourself) the screenreader announcing the word 'section' before reading the content inside your <section> tag.
If that doesn't make logical sense then maybe you've got your items ordered wrong.
Check out aria region role.
I don't know exactly how screen readers read nested sections but if the logical
sections on your page don't have a hierarchy then your HTML shouldn't either.
eg. (this is meant to represent HTML structure)
GOOD
section aria-label="dogs"
section aria-label="labradors"
section aria-labels="terriers"
section aria-label="cats"
section aria-label="sphynx"
section aria-label="persian"
BAD
Section used solely to group two other sections, but without a real meaning of its own as a 'section'.
section style="display: flex; flex-direction: row"
section aria-label="news"
section aria-labels="sport"
HTML5 also allows for setups such as:
<section>
<header>Header of section</header>
<aside><ul><li></li></ul></aside><!-- previously known as sidebar -->
<footer>Footer of section</footer>
</section>
multiple times on the same page, so you don't have just the one header, it goes a lot deeper than this, but it's worth checking out.
Check out the http://gsnedders.html5.org/outliner/
An updated method (as far as I understand it) could be something like this:
<main id="content">
<div id="inner-wrapper">
<section>
<h1>Section Title</h1>
...
</section>
<section>
<h1>Section Title</h1>
...
</section>
</div>
</main>
main {
width: 100%;
...
...
}
#inner_wrapper {
max-width: 80%;
margin: 0 auto;
}
See: http://www.w3.org/TR/html-main-element/, http://www.sitepoint.com/html5-main-element/ or http://html5doctor.com/the-main-element/ for more info.