Web Design in a Nutshell, 3rd Edition

Character Entities

XHTML (as a function of XML) is extremely fussy about special characters such as <, >, and &. All special characters should be represented in the XHTML document by their character entities instead. Common character entities are listed in Table 10-3, and the complete list appears in Appendix C.

Character entity references should be used in place of characters such as < and & in regular text content, as shown in these examples:

<p> the value of A &lt; B </p>
<p> Laverne &amp; Shirley </p>

In places where it was common to use special characters, such as in the title of a document or in an attribute value, it is now necessary to use the character entity instead. For instance, the following worked just fine in HTML, despite being invalid:

<img src="puppets.jpg" alt="Crocco & Lynch">

But in XHTML, the value must be written like this:

<img src="puppets.jpg" alt="Crocco &amp; Lynch" />

This applies to ampersands that occur in URLs as well.

<a href="mailto: [e-mail] ? subject=subject&amp;cc=person ">
     Email Jen<a/>