Hiding JavaScript code from older browsers

It is straighforward, follow the steps below:

1. Immediately after the opening <script> tag, put a one-line HTML-style comment without the closing characters, so that the first two lines of your script would look like this:

<script language="JavaScript">
<!--


2. At the end of your script, put the following two lines:

//-->
</script>


Thus, your HTML file will contain the following fragment:

<script language="JavaScript">
<!--
Here you put your JS code.
Old browsers will treat it
as an HTML comment.
//-->
</script>

Old browsers will treat your JS code as one long HTML comment. On the other hand, new JavaScript-aware browsers will normally interpret JS code between the tags <script> and </script> (the first and last lines of your JavaScript code will be treated by the JavaScript interpreter as one-line comments).