The reporting engine is optimized to work with newer browsers, thus the IE9+ requirement is not only for the viewer, but for the HTML rendering
used to display its content. There are added fallback mechanisms to provide support for HTML5 non-compliant browsers.
For more details, please refer to your support ticket on the same topic.
New HTML5/JS REPORT VIEWER with MOBILE AND TOUCH SUPPORT available in Telerik Reporting Q3 2013! Get the new Reporting version from your account or download a trial.