'Fusion' is null or not an object

[jojo]

I am trying to develop the mapguide but I am getting error "'Fusion' is null or not an object" for the below code.\[code\]<script type="text/javascript" src="http://stackoverflow.com/lib/OpenLayers/BaseTypes/Map.js"></script><script type="text/javascript" src="http://stackoverflow.com/layers/MapGuide/MapGuideViewerApi.js"></script><script type="text/javascript" src="http://stackoverflow.com/layers/MapGuide/MapGuide.js"></script><script type="text/javascript" language="javascript"> //parent.document.getElementById('Map').widget.aMaps[0].drawMap(); // set isFusion to false if you are using Ajax viewer var isFusion = true; function RefreshMap() { if (isFusion) { //Refresh(); Fusion = window.top.Fusion; //following code does not work //var legend = Fusion.getWidgetById("Legend"); //legend.renderer.update(); //reload the Map to refresh legend Fusion.getWidgetById('Map').reloadMap(); } else { // for basic web layout, // if using basic weblayout, referenceing // to MapGuideViewerApi.js should be removed parent.parent.Refresh(); } }</script>\[/code\]I have taken the code form below link http://adndevblog.typepad.com/infra...ibility-of-layer-in-fusion-does-not-work.html