<!-- Putting jQuery into no-conflict mode. --> <script src="prototype.js"></script> <script src="jquery.js"></script> <script> var $j = jQuery.noConflict(); // $j is now an alias to the jQuery function; creating the new alias is optional. $j(document).ready(function() { $j( "div" ).hide(); }); // The $ variable now has the prototype meaning, which is a shortcut for // document.getElementById(). mainDiv below is a DOM element, not a jQuery object. window.onload = function() { var mainDiv = $( "main" ); } </script>