Recently we faced an issue on ASP.NET application talking to CRM 2013, where document mode was always needed to be set to IE 9 in order for the UI elements and website controls to work properly. So, was digging on it and found the following way of doing it, add this to web.config:

<system.webServer>

<httpProtocol>

<customHeaders>

<clear />

<add name=”X-UA-Compatible” value=”IE=9″ />

</customHeaders>

</httpProtocol>

</system.webServer>

Following are possible values (referred from MSDN):

X-UA-Compatible value

Document modes

IE=5

Quirks mode

IE=7

IE7 mode

IE=8

IE8 mode

IE=9

IE9 mode

IE=10

IE10 mode

IE=11

IE11 mode

IE=edge

The highest supported document mode of the browser

IE=EmulateIE7

IE7 mode (if a valid <!DOCTYPE> declaration is present)

Quirks mode (otherwise)

IE=EmulateIE8

IE8 mode (if a valid <!DOCTYPE> declaration is present)

Quirks mode (otherwise)

IE=EmulateIE9

IE9 mode (if a valid <!DOCTYPE> declaration is present)

Quirks mode (otherwise)

IE=EmulateIE10

IE10 mode (if a valid <!DOCTYPE> declaration is present)

Quirks mode (otherwise)

IE=EmulateIE11

IE11 mode (if a valid <!DOCTYPE> declaration is present)

Quirks mode (otherwise)

Hope it helps!