I was playing with IE9 "Browser Mode" and "Document Mode" for Diagramo
As things were not looking nice I added Diagramo (local development url) to "Compatibility View"
and forgot about it.
A few days after tried to play with html5 features again but could not get out of "Browser Mode" : IE9 Compatible .... for 1 hour (damn)....when I realized that the whole site was added to IE9 "Compatibility View" list.
Remove it from "Compatibility View" list
Simple. Go to Tools (if menu bar not present, go to title bar, right click and activate menu bar) --> Compatibility View Settings --> remove your site.