HTML5 templates are based on HTML5 Canvas element. So far, most modern browsers , including Firefox, Chrome, Safari, Opera, IE9, etc. can support HTML5 functions. As to Chrome or Opera, it doesn't allow to load local XML files, thus you can't use Chrome or Opera to preview the slideshows saved in local disk, the preview will be OK after you upload them to your servers.
If you want to load the local XML file for Chrome or Opera, please refer to the following tutorial and reset for your web Browser: http://www.photo-flash-maker.com/html5-slideshow-preview.html.