The Rules of Xhtml

How does xhtml differ from html ?
These are the main xhtml rules. Consult www.w3c.org for a complete list.

Html vs xhtmlHtmlxhtml
1. Tags and attributes must be in lower case <TD BGCOLOR=ffcc33> <td bgcolor="#FFCC33">
2. Attribute values must be quoted
(see above example bgcolor="#FFCC33")		   
3. Elements must nest, no overlapping.
This is actually illegal in html as well but tolerated by most browsers.		 <B><I>text</b></i> <b><i>text</i></b>
4.All elements must be closed
(Note even the so-called empty img tag has a closing /
Commonly used empty tags include <hr /> <br />) 		Some text<p><img src="rose.gif" alt='rose'> <p>Some text</p><img src="rose.gif" alt='rose' />
5. Attribute value pairs cannot be minimized <TD nowrap> or <table border> <td nowrap="nowrap"> or <table border='1'>

6 Styles and scripts are best accessed by calls to external files

7 The DOCTYPE, head sections and title tags are mandatory
There are three DOCTYPES allowed Strict, Transitional and Frameset (for framesets only)
Here is a sample of the Transitional DOCTYPE

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head> <title> Minimal xhtml Document</title></head>