In doing browser compatibility testing in a new web form I was developing on my PC this morning, the form looked great in all browsers I had on my local Windows 8.1 PC – except for Internet Explorer 11, where it looked awful: div and form field border corners were squared instead of rounded, form fields rendered with excess height, some text was slightly truncated, and a few other issues.
When I looked at the CSS styles in use on the page in IE11’s built-in F12 developer tools, I noticed that the border-radius property on my form’s enclosing div was present, but it was missing its enable/disable checkbox, and the name of the style was shown with a red squiggle underline, as though IE didn’t recognize it. It seemed almost as though IE11 was behaving like a legacy browser that didn’t recognize that newer CSS property.
In fact, that did turn out to be exactly the problem. IE11 was rendering the form (running on my local IIS) with its legacy “Compatibility View” engine, which it is by default configured to do for intranet sites. (Oddly, my IE11 was not using Compatibility View to render another copy of the form that I was trying to use to debug the issue that I had IE loading via the “localhost” domain, which had me confused for a while.)
The solution was to disable IE11’s Compatibility View for intranet sites by doing Setting (gear icon) > Compatibility View Settings > uncheck “Display intranet sites in Compatibility View” checkbox. Making that configuration change immediately got IE11 to start rendering the page properly.