I'm currently working on developing a site, and I can't figure out why the text displays bigger in IE10 than it does in Chrome. (I've made sure that both of the browsers are set to 100% zoom--no more, no less.)

I've got a reset in my CSS: body { font-size: 1em; }. In Chrome (v27.0.1453.116 m), this displays as expected--if I change that rule in the CSS to font-size: 100%; or font-size: 16px;, nothing visibly changes. This, to me, indicates that in Chrome, 1em = 16px. But the proportional font-sizes (em and %) display much bigger in IE, at what appears to be 1em = 21px.

I have two images show the difference when body { font-size: 1em; }, but since I don't have 10 reputation yet, I can't post the full URLs. They're hosted on imgur, though, and their filenames are as follows:

  • font-size: 1em; in Chrome:

enter image description here

  • font-size: 1em; in IE10:

enter image description here

If I set font-size using px, then I get consistent results--both Chrome and IE10 will display consistently. But using px for font sizes strikes me as less-than-preferred practice these days.

You can see the HTML and the CSS in this jsFiddle I made. I included all of the CSS, which may have been a little unnecessary, but I thought it'd be better to provide more context rather than less.

Can anyone help me figure out why IE10's displaying 1em bigger than Chrome, and what I can do about it?

Thanks a bunch.

EDIT - Figures that as soon as I posted this elaborate question, I'd figure out what was going on. I had set the IE

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