Q:

javax.faces.view.facelets.FaceletException: The string "--" is not permitted within comments

When try to add a TODO comment in a piece of JavaScript code in a Facelets file like that  
<script type="text/javascript">
    <!--

    // TODO -- my comment
    function makeExecute() {                            

    }                       

    -->
</script>

then I face an exception:
javax.faces.view.facelets.FaceletException: Error Parsing /myScreen.xhtml: 
    Error Traced[line: 448] The string "--" is not permitted within comments.
        at com.sun.faces.facelets.compiler.SAXCompiler.doCompile(SAXCompiler.java:390)
        at com.sun.faces.facelets.compiler.SAXCompiler.doCompile(SAXCompiler.java:364)
        at com.sun.faces.facelets.compiler.Compiler.compile(Compiler.java:122)

How is this caused and how can I solve it?

A:

The stacktrace pretty much says it:

The string "--" is not permitted within comments.

As per definition: 

A comment declaration starts with <!, followed by zero or more
  comments, followed by >. A comment starts and ends with --, and
  does not contain any occurrence of "--".

To get rid of the error, simply type a space between the -- in the comment (or remove it).
// TODO - - my comment

