Many years ago, when HTML3 and 4 were still widely used in the mid to late 1990s, it was a common practice to place HTML style comments, or in some cases CDATA comments inside the SCRIPT tag in an attempt to hide that content from browsers that could not process it. In those browsers the content (javascript source code) would sometimes be displayed on the page, making it quite a mess.
This practice is now obsolete, and often problematic as there are very few of those browsers in use today – primarily only for testing of legacy functionality.
Example of old approach
<script type="text/javascript">
<--
// some script
-->
</script>
NOTE: for XHTML or XML documents, the use of a CDATA style comment is still required.
<script type=”text/javascript”>
//<![CDATA[
…code…
//]]>
</script>
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