There is no problem, but I need to delete temporary internet files, offline webpages after every preview, otherwise preview doesn’t work properly sometime. Try to delete temporary internet files, offline webpages from your browser, (CTRL+SHIFT+DEL) and run preview again. If manipulation of Z order still doesn’t work, check my example of increment Z order on every mouse click: drive.google.com/file/d/0B1sXiY … sp=sharing
You don’t have this refresh issue with Firefox.
Try to switch to it when you work with HTML5. Mozilla’s browser is a lot more friendly with HTML5 apps.