How to Enable Enterprise Mode in Internet Explorer 11

Another interesting, useful and hidden feature introduced in Internet Explorer 11 is the "Enterprise Mode" which has been implemented to provide better support for websites having compatibility issues in IE11 web browser.
Basically Enterprise Mode in IE11 tries to behave like IE8 version so that older websites which can recognize IE8 but can't recognize the new IE11 version, can open properly in IE11. Enterprise Mode in IE11 replicates original IE8 user agent string and outputs IE8's response to ActiveX controls and other binaries query so that old websites can open perfectly in IE11.
Enterprise Mode also brings back many deprecated features of IE8 such as CSS Expressions, etc for websites which contain objects or legacy web apps requiring those features to run. Enterprise Mode also turns off preloading website content feature of IE11 because some old websites do not support this feature. Basically you can consider Enterprise Mode as an emulation of IE8 web browser within IE11 which uses a modified browser configuration to open incompatible websites.
Enterprise Mode in IE11 is disabled by default but interested people can enable it using following methods:

• METHOD 1: Using Group Policy Editor (gpedit.msc)
• METHOD 2: Using Registry Editor (regedit.exe)

Credit: http://www.askvg.com