The Compatibility View button, introduced first in IE 8, is a button in address bar that when pressed, can quickly turn a IE 8 or later incompatible site work properly in a later version of IE. It’s useful to those who haven’t had time making their site modern IE user friendly but unfortunately it’s disappeared in IE11.
It’s go, and you won’t see it existed in IE’s address bar anymore.
So, why it’s removed in IE 11?
According to this Microsoft Technet document,
the Compatibility View button would attempt to fix a broken standards-based website, by getting the page to appear like it did in Internet Explorer 7. Today however, more standards-based websites are broken by attempting to appear like they did in Internet Explorer 7. So instead of implementing and using Compatibility View, developers are updating their server configuration to add X-UA-Compatible meta tags, which forces the content to the “edge”, making the Compatibility View button disappear. In support of these changes, the Compatibility View button has been completely removed for Internet Explorer 11.
And here is what you can do, if you still want it
While a site is up, click on the Gear icon at the top right corner of your IE window and choose Compatibility View settings.
And click OK to add the domain name into the website list that IE will be turning on Compatibility View automatically for you.
I have to admit that it’s cumbersome to use but unfortunately that’s the only way that turns a site in compatibility view in IE 11.