This is probably going to be the most viewed page of my XHTML section. It shows how to convert your current pages from HTML into XHTML. A lot of the information is the same between the two types of coding and many of the differences you may have already started doing.

In HTML, there are many tags that may be omitted and still be considered as good coding. These include some ending tags of a set (such as the td tag) or foundation ones (such as the head and body tags). XHTML will not allow this. All main foundation tags and all closing tags must be included.

Tag and property names must be written in lowercase letters. Since XML is case-sensitive, XHTML tag and property names must be written in lowercase. Property values may still be any case you want.

wrong:
<Code
  language="html"
  text={`<TD BGCOLOR="#FF0000">`}
/>

correct:
<Code
  language="html"
  text={`<td bgcolor="#FF0000">`}
/>


All tags must nest properly, no overlapping. Some browsers don't care if you overlap elements even though it is considered bad HTML coding. With XML and XHTML, you need to close the tags in reverse order. (last opened = first closed)

wrong:
<Code
  language="html"
  text={`<b> Bold text <i> and italics too </b> </i>`}
/>

correct:
<Code
  language="html"
  text={`<b> Bold text <i> and italics too </i> </b>`}
/>


All tags, including empty tags) must have a termination or ending tag. Regular tags such as the P or LI tag are commonly used on their own without an ending tag. XML and XHTML must include the ending tags for all of the tag sets. Empty elements (those without a closing tag) have no content.

Empty tags are the special single tags such as **br, hr, img, link and meta**. Since these do not come as a set, a termination must be specified within the tag itself. This is done by entering a space and forward slash into the tag. Examples:

<Code
  language="html"
  text={`<br />
<hr />
<img src="somepic.gif" />`}
/>

Technically, there isn't supposed to be a space before the forward slash, but it is needed for todays browsers to recognize it. The space is supported by the W3C standards for conformance.

Other tags affected by this are: **area, base, frame, input, and option**.

Property values must be quoted. If you follow good HTML coding practice, then you are probably already doing this. Every value must be quoted, even if it's numeric.

wrong:
<Code
  language="html"
  text={`<img src="somepic.gif" border=0>`}
/>

correct:
<Code
  language="html"
  text={`<img src="somepic.gif" border="0" />`}
/>

(Notice the use of the termination in the correct example too)

Tag properties cannot be minimized. There are some tag properties that are stated as a single word without a value assigned to them. XHTML requires that each property must have a quoted value assigned to it. Examples:

wrong:
<Code
  language="html"
  text={`<option value="myvalue" selected>
<input type="radio" name="Myname" checked>`}
/>

correct:
<Code
  language="html"
  text={`<option value="myvalue" selected="selected" />
<input type="radio" name="Myname" checked="checked" />`}
/>


For any pages using a nested list area, the inside list must be contained within a **LI**ne tag set.

<Code
  language="html"
  text={`<ol>
  <li> some info </li>
  <li> some info </li>
  <li>
    <ol>
    <li> other stuff </li>
    <li> other stuff </li>
    </ol>
  </li>
  <li> some info </li>
</ol>`}
/>

Notice the use of the ending LI tags as well.

For any **style** or **script** areas (that is CSS and JavaScript), take out the comment tags surrounding the scripts. These comment tags are usually entered before and after the script/styles to hide them from older browsers. Considering most people have a browser version 4 or higher these days, these aren't necessary anyways. The W3C actually recommends using external styles/scripts if possible instead of having them embedded.

Learn about how you'd convert your HTML to XHTML.

Conversion From HTML to XHTML

Validating an XHTML document's content involves checking its markup against a DTD and reporting markup errors. You can validate HTML, XHTML, and CSS files by using the W3C's validator. It will allow you to validate files on the Internet or on your computer.

The validator program will go through your coding, find any errors, and create a report. You can then "clean up" your coding and validate again. This service is free.

http://validator.w3.org/

You can also check your external CSS pages through the CSS validator ...

http://jigsaw.w3.org/css-validator/

Once validated as well formed coding, the bottom of the report page will show an icon image that you may display on your page such as the ones you see in the right side column of my site. Display it with pride!

Learn about how you can validate your XHTML.

Validation

Document Type Definitions (DTD) of XHTML coding is the same as the DTD of HTML coding. If you venture into learning XML, you will also be learning about creating an actual DTD file. For the purposes of a regular XHTML document, a standard DTD from the W3C can be used.

The DTD tag goes at the start of your coding before the starting html tag. There is no closing tag or termination for the DTD tag.

There are 3 Doctypes usable by an XHTML document. Strict, Transitional, and Frameset. The doctype is used when validating an XHTML document's content against a DTD and reporting markup errors. (The DOCTYPE lines below are broken in parts only to prevent the examples from being too wide for non-horizontal scrolling - you can keep it all on one line).

**XHTML 1.0 Strict**

Use this when you want really clean markup, free of presentational clutter. Use this together with Cascading Style Sheets.

<Code
  language="html"
  text={`<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">`}
/>

**XHTML 1.0 Transitional**

Use this when you need to take advantage of HTML's presentational features because many of your readers don't have the latest browsers that understand Cascading Style Sheets.

<Code
  language="html"
  text={`<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">`}
/>


**XHTML 1.0 Frameset**

Use this when you want to use HTML Frames to partition the browser window into two or more frames.

<Code
  language="html"
  text={`<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">`}
/>

Learn about what the various doctypes of XHTML are and how you'd use them.

XHTML Doctypes

**How is XHTML better than HTML? Why would you want to use XHTML?**

* to be able to take advantage of new coding techniques
* problems with the earlier versions have been fixed.

XHTML is a fairly close copy of HTML 4.01, so as far as tag functionalities go, so do not expect anything too new and fancy.

The W3C reasons for upgrading are extensibility and portability:

* **Extensibility**: Under HTML, the addition of a new group of elements requires alteration of the entire DTD. XML greatly eases the integration of new element collections as it is a subset of SGML itself and specifies it's own DTD.

* **Portability**: By the year 2002 as much as 75% of Internet access could be carried out on non-PC platforms such as palm computers, televisions, fridges, automobiles, telephones, etc. In most cases these devices will not have the computing power of a desktop computer, and will not be designed to accommodate ill-formed HTML as do current browsers.

Currently, the Netscape browser helps greatly for testing web pages by displaying blank or broken pages when it comes across sloppy coding. IE is the most forgiving browser and will show almost any page no matter the extent of coding errors.

While HTML itself isn't completely lacking in extensibility or portability but the evolution of it has been extremely slow compared to the pace of Internet development. This fuels the problems encountered trying to make your pages work on a wide range of browsers and platforms. XHTML will help to remedy those problems.

**So What's Wrong with HTML?**

Since 1990, HTML has been the main set of codes to make a document displayable on the World Wide Web. It has gone through several revisions, and is now at version 4.01. Although it has been extremely successful, this coding will eventually be succeeded by XHTML. HTML will not go through another revision, except as an application of XML (XHTML).

HTML will still be around for many years though. It has established itself as a strong and well used coding structure.

Learn about the differences between HTML and XHTML.

XHTML vs HTML

## What is XHTML?

* XHTML stands for e**X**tensible **H**yper **T**ext **M**arkup **L**anguage.
* It is aimed to replace HTML.
* It is almost identical to HTML 4.01
* It is the reformulation of HTML 4.01 as an **application** of XML.
* It is a stricter, tidier version of HTML.
XHTML 1.0 is the next level of coding as specified by the W3C.

XHTML is a transition / combination of HTML and XML. To change from HTML to XHTML requires just a few changes in your coding styles. The main page to check out is **CONVERTING** but all the others provide valuable information about this coding technique as well.

XHTML provides the framework for future extensions of HTML and aims to replace HTML in the future. Some resources refer to XHTML as HTML5.

XHTML 1.0 became an official W3C recommendation on January 26, 2000. A W3C recommendation means that the specification is stable, that it has been reviewed by the W3C membership, and that the specification is now a Web standard.

XHTML 1.0 is the first step toward a **modular** and **extensible** web environment based on XML (eXtensible Markup Language). It provides the bridge for web designers to use a future based coding and still be able to maintain compatibility with today's browsers.

**SGML** stands for **S**tandard **G**eneralized **M**arkup **L**anguage. Simply put, it is the very root coding of coding. HTML is an application of SGML. XML is a simplified subset of SGML.

**DTD** stands for **D**ocument **T**ype **D**eclaration. It is a set of instructions that states what tags are usable and what (re)action they create. Each browser has a DTD set in it's programming set by the browser companies. This is how some tags will work in only one type of browser or version. It has the tags stated in it's DTD. XML makes it possible to create unique tag sets by applying it's own DTD. This makes the DTD more compatible with more browsers.

Learn about XHTML and what it aims to do.

XHTML

Author

What is XHTML?

Table of Contents

Learn More About XHTML