If you have a global navigation with more than a few second level items then the fly-out nature of the menu may cause some page content to be hidden while the menu is being interacted with by users. This is expected and acceptable behaviour.
I have found that sometimes (in IE only) the navigation fly-out falls behind page elements and cannot be used correctly. This is the case when iFrames are present in the content area. This issue came to my attention when using the Yammer Embed API to provide users with Yammer feeds from SharePoint.
The simplest way to resolve this is with CSS. The following CSS snippet should resolve this issue for you. We all know about
z-index but the
position:relative is also required for it to be applied correctly in IE.
N.B. The below snippet is specifically for Yammer Embed iFrames, if you would like to target all iFrames then the id selector should be removed (i.e.