Consider the following scenario. You have a webpage that contains an iframe with scrollbars, and an HTML page is displayed within the iframe. In this scenario, the content of the iframe may get rendered on top of the scrollbars.
This problem can occur if Windows Internet Explorer is using Quirks mode as the document mode.
Microsoft has confirmed that this is a problem in the products listed in the Applies-to section of this article. To work around this issue, use Standards Mode for Windows Internet Explorer 8 or Internet Explorer 9 to render the web page.
This issue only occurs if the page is either using no document type declaration or is using a faulty document type declaration. This puts the browser into Quirks mode. Quirks mode follows non-standard rules introduced with Internet Explorer 5.5 and is still available for backwards compatible with legacy web pages that expect the non-standard behavior. Microsoft recommends using the latest available standard mode to render HTML pages.
iframe, scrollbar, quirks mode, standards mode