I'm trying to test a website on IE8, While i don't have IE8 on my computer i use Developer tools (f12) and document mode to imitate IE8, But it doesn't work, The browser isn't loading the alternative CSS file.
Conditional comments do not work in IE 11, even when using compatibility mode. If you need to test CSS for outdated versions of IE you really need to download a free VM from http://modern.ie. There are 90 to choose from so there should be one you can run locally or in the cloud.