Hi Ken,
I don't think you understand the issue.
1em = the size of the parent object's font. In most browsers it is defaulted to 16, although this can be changed by user preference on the browser or within the program itself.
So if I set height="300em", in IE and firefox it is going to give me an editor that is about 4800px tall, which is not acceptable.
The issue as I see it is the latest version of CE doesn't convert properly from em to px.
If I go back to the version dated 10/14/2010 and run the same text in Chrome, it does convert the em to px properly:
<CE:Editor id="Editor1" AutoConfigure="Simple" runat="server" Height="7em" ></CE:Editor><br />
<table cellspacing="0" cellpadding="0" _iscuteeditor="True" id="CE_Editor1_ID" style="background-color: rgb(244, 244, 243); border-top-color: rgb(221, 221, 221); border-right-color: rgb(221, 221, 221); border-bottom-color: rgb(221, 221, 221); border-left-color: rgb(221, 221, 221); border-top-width: 1px; border-right-width: 1px; border-bottom-width: 1px; border-left-width: 1px; border-top-style: solid; border-right-style: solid; border-bottom-style: solid; border-left-style: solid; width: 780px; height: 112px; ">
With the latest it doesn't.
<table cellspacing="0" cellpadding="0" _iscuteeditor="True" id="CE_Editor1_ID" style="background-color: rgb(244, 244, 243); border-top-color: rgb(221, 221, 221); border-right-color: rgb(221, 221, 221); border-bottom-color: rgb(221, 221, 221); border-left-color: rgb(221, 221, 221); border-top-width: 1px; border-right-width: 1px; border-bottom-width: 1px; border-left-width: 1px; border-top-style: solid; border-right-style: solid; border-bottom-style: solid; border-left-style: solid; height: 7px; width: 780px; ">