When you include your own JavaScript functions in a page or component, you have to take care that the formatting doesn't go awry. So I recommend you use the following approach (pay special attention to the comment tags at the start and end of the script tags):
<script type="text/javascript" language="JavaScript"> var myValue = '${prop:value}'; // before the comment so Tapestry sees it! <!-- // // Toggle the display of a set of elements between show and hide function toggle() { for ( var i=0; i < arguments.length; i++ ) { $(arguments[i]).style.display = ($(arguments[i]).style.display != 'none' ? 'none' : '' ); } } // --> </script>