why compatibility mode for intranet sites

Question

I\'m a Mac person, web designer, trying to understand \"Display intranet sites in compatibility mode\" option with IE 11

I have client, an architecture firm, that used

Answer 1

I have upvoted the other answer, so i'm not really fishing for your vote. I just wanted to add the findings that i had this evening.

I have a state of the art HTML5 website, that works well in every browser. However, in my own local environment IE is messing thigns up like you said, and even worse. I was thinking it was a server issue as the html that was passed as a responsetext from my server was the right HTML. however, IE was parsing it to something different ( I usually think of IE as a great browser, but I really lost it)

this structure:

became this in the DOM:

As you can see the whole DOM was parsed into something completely different and was not working, thanks to compatibility being enabled for the intranet. I did set the doctype, and validated my site on w3c, so that wasn't the problem either. The bottomline is, compatibility mode is something you want to stay away from as a developer.