IE Compatibility

Different versions of IEs render web pages differently. That causes headache for web developers. Microsoft provides a compatibility solution for the old web sites. Since IE 8, the Internet Explorer browsers start to handle the X-UA-Compatible Meta Tag or HTTP response header. The web server can send it to tell the IE to render the web document in an older IE mode.

This link gives a detailed description of X-UA-Compatible: https://msdn.microsoft.com/en-us/library/ff955275%28v=vs.85%29.aspx

The values of X-UA-Compatible are:

• IE=5
• IE=7
• IE=8
• IE=9
• IE=10
• IE=11
• IE=edge
• IE=EmulateIE7
• IE=EmulateIE8
• IE=EmulateIE9
• IE=EmulateIE10
• IE=EmulateIE11

The difference between IE=7 and IE=EmulateIE7 is that IE=EmulateIE7 wil determine whether to use IE7 mode or IE5 (Quirks) mode by the !DOCTYPE declaration.

This link explains the !DOCTYPE declaration and the IE modes: https://msdn.microsoft.com/en-us/library/ff955379%28v=vs.85%29.aspx

IE also provides a Compatibility View List that an end user can manually add a site to make it be rendered as EmulateIE7. Users can also control to display all local intranet sites or even all web sites in EmulateIE7 mode. (https://msdn.microsoft.com/en-us/library/ff955410%28v=vs.85%29.aspx)

Another very good article about this topic: https://sharovatov.wordpress.com/2009/05/18/ie8-rendering-modes-theory-and-practice/.