Decreased rendering performance in Internet Explorer when adjusting zoom level in Quirks mode
Content provided by Microsoft
Applies to: Internet Explorer 10Windows Internet Explorer 9
Most web browsers will switch to Quirks Mode if a web page uses non-standard HTML document declaration. Apart from most non-Microsoft web browsers, Windows Internet Explorer uses a Quirks Mode rendering engine which is not based on a Standards Mode rendering engine. The Quirks Mode rendering engine for Windows Internet Explorer is based on Windows Internet Explorer 5.5. It was first introduced with Windows Internet Explorer 6 for backwards compatibility with legacy web pages.
Quirks Mode is not aware of page zooming, a feature which has been available since Windows Internet Explorer 7. Quirks Mode has not received any performance improvements to maintain backwards compatibility for page zooming. As a result, poor performance may be detected when using page zooming on web pages when using Quirks Mode.
This behavior is by design when Quirks Mode gets used. It is recommended to use the most current Windows Internet Explorer standards mode, which is not affected by this page zooming issue.
More information on Windows Internet Explorer document modes can be found at the following locations: