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Fotiman - 2:35 pm on Dec 22, 2011 (gmt 0)
<!DOCTYPE html>
<html>
<head>
<style>
#base {
font-size: 62.5%;
}
#increased {
font-size: 1.2em;
}
#twelvepx {
font-size: 12px;
}
</style>
</head>
<body>
<div id="base">
<div id="increased">
The quick brown fox jumped over the lazy dog.
</div>
</div>
<div id="twelvepx">
The quick brown fox jumped over the lazy dog.
</div>
</body>
</html>
That example shows that your calculation was correct. 62.5% of the default (16px) = 10px. 10px * 1.2em = 12px. Viewing the example above will show that both lines look the same. The problem is simply that 12px is just too small for most text.