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HTML, XHTML, XML (HTML5, too!)

XML is a markup language that allows you to create your own custom tags enabling the transmission of data between applications and organizations. XHMTL, short for Extensible Hypertext Markup Language, is a hybrid of HTML and XML.

Writing XHTML isn't difficult. The hardest part is breaking a few habits. One very important thing to remember when writing XHTML: use the correct tag to mark up your code. For instance, if it's a paragraph, surround the text with paragraph tags. Don't just drop it on the page and put two break elements after it.

Additional guidance for writing good mark-up | What about HTML5?

The following tips will help you make sure that your HTML code conforms with XHTML recommendations.

1. (If you're using Dreamweaver:) Set up Dreamweaver to code with XHTML 1.0 Strict. Edit the following settings.
   • Edit > Preferences > New Document. Find the field labeled Default Document Type (DTD) and select XHTML 1.0 Strict.
   • Edit > Preferences > Validator. Select the XHTML 1.0 Strict checkbox.
2. All elements (tags) and attribute names must be in lowercase.
   • <blockquote cite="http://www.americanrhetoric.com/speeches/Ihaveadream.htm"> <p>And so even though we face the difficulties of today and tomorrow, I still have a dream.</p> </blockquote>
   • The element is blockquote, with a start tag and an end tag in lowercase.
3. All attributes names must have values, and those values must be quoted.
   • <a href="xyz.html" title="Link to xyz document">
   • a is the element, with href and title attributes. All in lowercase and quoted.
4. Close all elements.
   • Example: <li>some text here</li>
5. Empty elements must end with />.
   • Example: <br/> or <hr/>.
   • Example: <img src="flower.gif" alt="flower"/>
6. Properly nest all of your code:
   • Example: <p><b>This is correct</b></p>
   • Example: <b><p>This is INCORRECT</b></p>
7. No double dashes within a comment tag.
   • Example: <!-- This is correct - and proper -->
   • Example: <!-- This is INCORRECT -- and may cause problems-->
8. Encode all ampersand (&) and less-than (<) signs with & or <. Code for other common HTML entities are easily found .
   • When using a character or numeric entity, be sure to close it with a semicolon.
9. For links in the same page, use id, rather than name.
   • Link to another part of the page: <a href="#section2">Section 2</a>
   • Where the link should point: <h2 id="section2">Section 2</h2>
   • Note that you can use id within any element to uniquely identify it. Once an element has that unique identifier, you can point to it with an anchor link. See the markup for the "Top of Page" link for another example.
10. Validate! Use the W3C validator . Validation is an excellent way to find errors in your markup.

Additional guidance for writing good mark-up.

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Guidance for Good Markup

To view the example usage for any item within this document, please view the source.

• Header Examples
• Link Examples
• Paragraphs
• Inline Text
• Lists

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Header Examples

The main page title (heading) of this guide is a heading 1 (h1) element. Reserve h1 for individual page titles only (like "Markup Guide" above).

The secondary header ("Header Examples") is an h2 element, which may be used for any form of important page-level header. More than one may be used per page. Consider using an h2 unless you need a header level of less importance, or as a sub-header to an existing h2 element. Any header level may include links.

Third-Level Header

The header above is an h3 element, which may be used for any form of page-level header which falls below the h2 header in a document hierarchy. More than one may be used per page.

Fourth-Level Header

For all headers below third-level, follow the guidelines listed above. Only use lower header levels when necessary. I tend to use h4 in place of <p><strong>Your text here</strong></p>.

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Link Examples

External and internal links are handled differently.

External links

Internal links

Code EPA internal links as usual. title attributes are not necessary, but helpful.

Example: <a href="http://www.epa.gov/internalURLhere/" />

Internal PDF links

Links to PDF documents. For more info, see EPA's PDF linking standard.

Anchor links

For links within pages, use id attributes, not name attributes (name is deprecated).

As an example of an anchor link, consider the "jump lists" in the "table of contents" above. Each link in the box is written <a href="#linkexamples">Link Examples</a>. Clicking on "Link Examples" brings you to the Link Examples heading, which is coded as <h2 id="linkexamples">Link Examples</h2>.

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Paragraphs

All paragraphs are wrapped in p tags. (If you have a quote, paragraphs can be wrapped within a blockquote element. EPA has a pull-quote standard, which can be use for the same purpose.)

Blockquotes

Historically, blockquote has been used purely to force indents, but this can now be achieved using CSS. Reserve blockquote for quotes. Here's an example of correct usage:

Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Cras euismod fringilla arcu. Integer posuere. Aliquam ipsum. Donec eget massa ac orci tempus euismod. Donec quis neque nec neque consequat sollicitudin. Donec commodo tempor nulla. Suspendisse venenatis. Ut ut leo. Nunc placerat urna at libero. Nunc suscipit lacus.

lipsum.com

Additionally, you might wish to cite the source, as in the above example. (The correct method involves the cite attribute directly applied to the blockquote element, but since no browser makes any use of that information whatsoever, it's useful to also specify the standalone cite element.)

EPA has a pull-quote standard, which can be used for the same purpose.

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Inline Text

There are a number of inline HTML elements you may use anywhere within other elements, including abbr, acronym, cite, code, del, em, ins, kbd, strong, and var.

abbr

Used for any abbreviated text, whether it be acronym, initialism, or otherwise. Generally, it's less work and useful (enough) to mark up only the first occurence of any particular abbreviation on a page, and ignore the rest. Any text in the title attribute will appear when the user's mouse hovers the abbreviation (although notably, this does not work in Internet Explorer). Example abbreviations and usage: NASA, HTML, and Mass.

acronym

Used for only specific abbreviations. Like abbr, any text in the title attribute will appear when the user's mouse hovers the acronym (unlike abbr, however, this does work in Internet Explorer. According to Mirriam Webster , acronyms are:

...a word (as NATO, radar [...] ) formed from the initial letter or letters of each of the successive parts or major parts of a compound term; also : an abbreviation (as FBI) formed from initial letters.

If you think the difference between acronym and abbr is esoteric, you're right.

code

Used for computer code samples. Useful for technology-oriented sites, not so useful otherwise. Example code and usage:

function getJello() {
  echo $bill_cosby_mugs;
}

Inline usage: just like elsewhere in this document, HTML elements like em or code can be considered code, and marked up as such.

cite

Used for defining a citation or reference to other information sources. Example cited text and usage: More information can be found in [ISO-0000].

del

Used for deleted or retracted text which still must remain on the page for some reason. Since the default style includes a strikethrough line, it's preferable to the s element. The del element also has a datetime attribute which allows you to include a timestamp directly in the element. Example deleted text and usage: She bought two five pairs of shoes. (Write the datestamp as so: datetime="2005-09-12".)

em

Used for denoting emphasized text. In most instances where you'd want to italicize text (using the HTML element i or otherwise) you should use the em element instead. Notable exceptions are stylistic italicizing of proper titles, foreign languages, etc. where italicizing is used for differentiation instead of emphasis. In those cases, no proper HTML elements exist, so an i element or a span element with a custom class may be preferable. Example emphasized text and usage: You simply must try the negitoro maki!

ins

Reserved for the "new!" javascript function.

kbd

Used for text which should be typed by the user. Mainly useful for computer instructions. Example keyboard text and usage: Please press Enter to continue.

strong

Used for denoting stronger emphasis than the em element. In most instances where you'd want to bold text (using the HTML element b or otherwise) you should use the strong element instead. Notable exceptions are stylistic bolding of examples, first occurences of names in an article, etc. where bolding is used for differentiation instead of emphasis. In those cases, no proper HTML elements exist, so b element or a span element with a custom class may be preferable. Example strong text and usage: Don't stick nails in the electrical outlet.

var

Used for variables within computer code snippets. Useful for technology-oriented sites, not so useful otherwise. Example code and usage: Add 5 to $result and recalculate.

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Lists

Then there are the lists. ul denotes an unordered list (ie. a list of loose items that don't require numbering, or a bulleted list). ol denotes an ordered list, and various numbering schemes are available through the CSS (including 1,2,3... a,b,c... i,ii,iii... and so on). Each item within the ul or ol requires a surrounding <li> and </li> tag, to denote individual items within the list (as you may have guessed, li stands for list item).

Example lists and usage:

• This is an unordered list.
• It has two items.

1. This is an ordered list.
2. It has two items.
3. No, I lied, it has three.

The Area Navigation (sidebar), the breadcrumbs, and the global footer are marked up as a list of links. You can see that it is possible to style each list in alternative ways.

Lists within lists are written as follows:

<ul>
  <li>List item
    <ul>
      <li>Sub-list item</li>
    </ul>
  </li>
</ul>

EPA has a standard for simple lists within the content.

Additionally, dl is another list type called a definition list. Instead of list items, the content of a dl consists of dt (Definition Term) and dd (Definition description) pairs. Though it may be called a "definition list", dl can apply to other scenarios where a parent/child relationship is applicable. For example, it may be used for marking up dialogues, with each dt naming a speaker, and each dd containing his or her words.

This is a term.

This is the definition of that term, which both live in a dl.

Here is another term.

And it gets a definition too, which is this line.

Here is term that shares a definition with the term below.

Here is a defined term.

dt terms may stand on their own without an accompanying dd, but in that case they share descriptions with the next available dt. You may not have a dd without a parent dt.

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Created by Dave Shea ; adapted by Michael Hessling.

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Is HTML5 Ready Yet?

HTML 5 is ready to work today. HTML5 works right now. Sure it's not 100% complete, but 99% of the elements are in place. Note that not all of the above rules will apply in HTML5.

It's the JavaScript stuff that's going to take a bit longer to get fully A-grade browser support, but there's a lot that's supported in the latest browsers.

Go check out http://html5demos.com for some of the JS that works now. If you want to learn more, head over to http://html5doctor.com for tutorials on getting started with HTML5 today.

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