As XHTML is an XML application, you will benefit from developments in the XML world. For example XML tools such as editors, converters, browsers, etc. can be used with XHTML resources. In addition there are developments to the XML family of protocols and formats which will provide additional functionality for XHTML.
Attributes values must be in double or single quotes
<ol type=1> becomes <ol type="1"> or <ol type='1'>
Every element must have an end tag, even when it doesn't really matter.
<br> <input type="text" value="Amazon.com" size="20" >
becomes <br /> <input type="text" value="Amazon.com" size="20" />
For compatibility with older browsers its best to put a single space before the '/'. Some browsers have trouble with "<br></br>" so its best to use "<br />"
How to convert most HTML pages to XHTML. 1. Heading lines at top At the beginning of documents we need to include a few lines:
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
The location of the dtd allows validating parsers to check the document. Most browsers will ignore these tags.
Every attribute must have a value
<ol compact> <input type="radio" name="title" value="decline" checked>decline</input>
becomes <ol compact="compact" > <input type="radio" name="title" value="decline" checked="checked">decline</input>
The XHTML modularization model defines the modules of XHTML. XHTML is a simple, but large language. XHTML contains most of the functionality a web developer will need.
For some purposes XHTML is too large and complex, and for other purposes it is much too simple.
By splitting XHTML into modules, the W3C (World Wide web Consortium) has created small and well-defined sets of XHTML elements that can be used separately for simple devices as well as combined with other XML standards into larger and more complex applications.
With modular XHTML, product and application designers can: * Choose the elements to be supported by a device using standard XHTML building blocks. * Add extensions to XHTML, using XML, without breaking the XHTML standard. * Simplify XHTML for devices like hand held computers, mobile phones, TV, and home appliances. * Extend XHTML for complex applications by adding new XML functionality (like MathML, SVG, Voice and Multimedia). * Define XHTML profiles like XHTML Basic (a subset of XHTML for mobile devices).
XHTML is not very different from HTML 4.01, so bringing your code up to the 4.01 standard is a good start. In addition, you should start NOW to write your HTML code in lowercase letters. . The Most Important Differences:
* XHTML elements must be properly nested * XHTML documents must be well-formed * Tag names must be in lowercase * All XHTML elements must be closed
Attributes values must be in double or single quotes <ol type=1> becomes <ol type="1"> or <ol type='1'>
Every element must have an end tag, even when it doesn't really matter. <br> <input type="text" value="Amazon.com" size="20" >
Some More XHTML Syntax Rules:
* Attribute names must be in lower case * Attribute values must be quoted * Attribute minimization is forbidden * The id attribute replaces the name attribute * The XHTML DTD defines mandatory elements
1. Attribute Names Must Be In Lower Case: This is wrong: <table WIDTH="100%">
This is correct: <table width="100%">
2. Attribute Values Must Be Quoted:
This is wrong:
<table width=100%>
3. Attribute Minimization Is Forbidden:
This is wrong: <input checked> <input readonly> <input disabled> <option selected> <frame noresize>
This is correct: <input checked="checked" /> <input readonly="readonly" /> <input disabled="disabled" /> <option selected="selected" /> <frame noresize="noresize" />
Here is a list of the minimized attributes in HTML and how they should be written in XHTML: HTML XHTML compact compact="compact" checked checked="checked" declare declare="declare" readonly readonly="readonly" disabled disabled="disabled" selected selected="selected" defer defer="defer" ismap ismap="ismap" nohref nohref="nohref" noshade noshade="noshade" nowrap nowrap="nowrap" multiple multiple="multiple" noresize noresize="noresize"
4. The id Attribute Replaces The name Attribute: HTML 4.01 defines a name attribute for the elements a, applet, frame, iframe, img, and map. In XHTML the name attribute is deprecated. Use id instead.
This is wrong: <img src="picture.gif" name="picture1" />
This is correct: <img src="picture.gif" id="picture1" />
Note: To interoperate with older browsers for a while, you should use both name and id, with identical attribute values, like this: <im
* 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.
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.
W3Schools was converted from HTML to XHTML. To convert a Web site from HTML to XHTML, you should be familiar with the XHTML syntax rules. Your pages must have a DOCTYPE declaration if you want them to validate as correct XHTML. The following DOCTYPE declaration was added as the first line of every page: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
Be aware however, that newer browsers might treat your document differently depending on the <!DOCTYPE> declaration. If the browser reads a document with a DOCTYPE, it might treat the document as "correct". Malformed XHTML might fall over and display differently than without a DOCTYPE.
Lower Case Tag And Attribute Names Since XHTML is case sensitive, and since XHTML only accepts lower case HTML tags and attribute names, a general search and replace function was executed to replace all upper case tags with lowercase tags. The same was done for attribute names. We have always tried to use lower case names in our Web, so the replace function did not produce many real substitutions.
All Attributes Were Quoted Since the W3C XHTML 1.0 Recommendation states that all attribute values must be quoted, every page in the web was checked to see that attributes values were properly quoted. This was a time-consuming job, and we will surely never again forget to put quotes around our attribute values.
Empty Tags: <hr> , <br> and <img> Empty tags are not allowed in XHTML. The <hr> and <br> tags should be replaced with <hr /> and <br />.
This produced a problem with Netscape that misinterpreted the <br/> tag. We don't know why, but changing it to <br /> worked fine. After that discovery, a general search and replace function was executed to swap the tags.
A few other tags (like the <img> tag) were suffering from the same problem as above. We decided not to close the <img> tags with </img>, but with /> at the end of the tag. This was done manually.
The Web Site Was Validated After that, all pages were validated against the official W3C DTD with this link: XHTML Validator. A few more errors were found and edited manually. The most common error was missing &l
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