IE6 displays larger font using em

I set in body font:62.5%/1.2 Arial,Helvetica,sans-serif; and then I use ems to size a font.

The problem is that IE6, and probably also IE7? displays font much larger.

Is that only IE6 bug or also IE7? Is the only way to insert ie6.css and put smaller numbers for ems if I want to use em as unit?

Thank you

Why? It’s much easier just to leave the standard font size alone, and then only make it larger or smaller for particular elements as you need them.