Overlapping elements are cloned
Overlapping formatting elements are cloned in Windows Internet Explorer 9 to reduce ambiguity in the Document Object Model (DOM).
Typically, a site looks the same with or without this feature.
However, if you perform DOM operations on elements that are overlapped in markup, the operations might not work the same way in Internet Explorer 9. For example, if you make DOM calls such as firstChild or nextSibling on an overlapped element, these calls might not work the same way.
Test your code by using the Internet Explorer Developer Tools to find and fix any overlapping elements.
Build date: 11/17/2013