The HTML Comment Tag

The HTML comment tag is used to add text to an HTML document without including that text in the Web page. When used in an ION Script page, HTML comment tags and the content they enclose are passed unchanged directly to the browser.

The HTML comment tag consists of the opening tag . Text between  will not appear in the Web page, nor will it be evaluated by the ION Script parser:

This comment will, however, be passed in the HTML file sent to the browser, and can be seen by viewing the page source (View

Source).

Comments can be used on a single line as shown above, or can span multiple lines as follows:

Documenting your code. Comments are useful in documenting your Web page or ION Script application, and can help clarify your ION Script code for you and other developers.

Debugging ION Script applications. Comments allow you to "turn off" selected ION Script tags by commenting them out, in order to test individual code segments. For example, to comment out an ION_EVALUATE tag, you would use the comment tag as follows:

<!-- <ION_EVALUATE EXPR="$A = 10"/> -->

Prevent content inside HTML tags from appearing as text in older browsers that do not recognize the tag. For example, the <STYLE> tag is not recognized by some older browsers, in which case the content inside the <STYLE> tag appears as text. The HTML comment tag is often used inside the <STYLE> tag to prevent style declarations from appearing as text in older browsers:

<STYLE type="text/css"><!--  
   H1 {color: red;}  
   BODY {background: yellow;}  
--></STYLE>

Similarly, because older browsers do not support scripting languages such as JavaScript and VBScript, HTML comment tags are often used inside <SCRIPT> blocks to prevent scripts from appearing as text in older browsers:

<SCRIPT TYPE="text/javascript">  
<!--  
   document.write("Hello World");  
//-->  
</SCRIPT>

Note
IDL code inside an <IDL>...</IDL> block can also contain comments, but IDL comment syntax is used in this case, not the HTML comment tag. For information on using comments in IDL code, see Commenting IDL Code.