WP 3.0 post editor width doesn’t work with Internet Explorer

I have been struggling with this too, and I managed to get the same effect by setting the right margin on the editor body. The right margin I calculate dynamically by using the IE-only “expression” property.

My code looks like this:

html .mceContentBody {
max-width: 544px;
margin-right: expression((document.body.offsetWidth – 580) + ‘px’);
}

As you probably have noticed, the number i subtract from the body width in the expression property is not the same as the max-width. I don’t know why, but this is necessary to make the content look the same in the editor and on the frontend.

So in your case, the code should probably look something like this:

html .mceContentBody {
max-width: 600px;
margin-right: expression((document.body.offsetWidth – 636) + ‘px’);
}