Microsoft Jscript runtime error: 'sys.Extended.ui' is null or not an object when convnerting from a web site to a web application

<div class="body"> I have read that you should move from a web site to a web application to optimize it.  I have painstakingly followed the Microsoft article: "Walkthrough: Converting a Web Site Project to a Web Application Project in Visual Studio ".  I am getting the error  "Microsoft Jscript runtime error: 'sys.Extended.ui' is null or not an object "  My suspicion is there's a problem with AJAX.  My error is: 
Sys.Application.add_init(function() {    $create(Sys.Extended.UI.HoverMenuBehavior, {"HoverCssClass":"HoverCSS","OffsetX":5,"OffsetY":5,"PopupPosition":4,"dynamicServicePath":"/Plant.aspx","id":"MainContent_GridView1_hmeItemDesc_0","popupElement":$get("MainContent_GridView1_PanelIt ...