There are three characters which should always appear in content as escapes, so that they do not interact with the syntax of the markup:

• &lt; (<)

• &gt; (>)

• &amp; (&)

You may also want to represent the double-quote (") as &quot; - particularly in attribute text when you need to use the same type of quotes as you used to surround the attribute value.

Escapes can be useful to represent characters not supported by the encoding you chose for the document, for example, to represent Chinese characters in an ISO Latin 1 document. You should ask yourself first, however, why you have not changed the encoding of the document to something that covers all the characters you need (such as, of course, UTF-8).

If your editing tool does not allow you to easily enter needed characters you may also resort to using escapes. Note that this is not a long-term solution, nor one that works well if you have to enter a lot of such characters - it takes longer and makes maintenance more difficult. Ideally you would choose an editing tool that allowed you to enter these characters as characters.

A potentially very useful role for escapes is for characters that are invisible or ambiguous in presentation.

One example would be Unicode character 200F: RIGHT-TO-LEFT MARK. This character can be used to clarify directionality in bidirectional text (eg. when using the Arabic or Hebrew scripts). It has no graphic form, however; so it is difficult to see where these characters are in the text, and if they are lost or forgotten they could create unexpected results during later editing. Using &rlm; (or its NCR equivalent &#x200F;) instead makes it very easy to spot these characters.

An example of an ambiguous character is 00A0: NO-BREAK SPACE. This type of space prevents line breaking, but it looks just like any other space when used as a character. Using &nbsp; (or &#xA0;) makes it quite clear where such spaces appear in the text.