“The site isn’t working with Internet Explorer 10!!!” yells my client through the IM window, to which I gave a WTF expression since I developed it under IE10 and it worked beautifully.
Wondering what kind of problem it could be I got him to open up a remote session so I could see what the problem was, sure enough the site was a mess, layouts were wrong, backgrounds were missing, it was as if the browser forgotten to download a few CSS files, so I hit F12 to bring up the developer tools and then I saw the problem.
For some reason his IE10 was in IE7 mode, which was outside of the support scope of the project (Thankfully!). So I switched it back to IE10, and everything looked and worked fine again.
So if someone is complaining that the site looks and works horribly in IE10 when it shouldn’t be, you might want to check if any of these compatibility settings are in effect!