У вашего броузера проблема в совместимости с HTML5
Learn how to use the Accordion Widget for Adobe Muse. View all the styling options and see how to apply more than one widget to each page and how it adapts to the size of your browser. No coding is required!
Developed by Responsive Muse
Download Widget: http://responsive-muse.com/product/accordion/
More Free and Premium Widgets here: http://responsive-muse.com/product-category/muse-responsive-widgets/