A detailed and articulate (also aptly titled) post on portal rendering issues in IE is already available. Portal consultants, admins and the likes should definitely read it to understand how the issue and its solution has evolved in depth. This document descibes what should be done when facing a rendering issue towards solving it.
1. Check if the issue can be reproduced in other browsers – Chrome and Firefox in particular
If the issue can be reproduced in other browser versions as well then it is not an IE rendering issue.
2.Get the necessary information
SystemInfo – NW version.SP level.patch level
Browser version – IE9, IE10, IE11 etc.
3. Check if the browser is compatible with your portal version here
4. Check if you have the patches applied as per note 1972506 if you are using IE11
5. Check if you have the patches applied as per note 2158358 if you are using the Classic framework page/ Classic framework page lite or a custom framework page based on it.
6. Check if you have the browser document mode property set as per 1458799
If you are using a custom framework page then make sure that the browser document mode iview is added to it.
7. Check if you have the patches applied as per note 1814711
8. Find out the rendering mode required by the application.
( UI5 iviews must be rendered in the standards mode if the portal framework page is being rendered in quirks mode )
If the application has to be rendered in the standards mode then set the iview property “Launch in new window” to “Display in separate headerless portal window ( standard mode)” , i.e. navmode 10.
If navmode 10 is not available then you will have to follow note 1737445
9. If you would like to open content that requires standards mode rendering within the portal content area then the Ajax Framework Page Standards mode can be used described in note 2001910 which has some restrictions.