Now using a CSS hack for IE's "filter" attribute to prevent CSS warnings in Firefox
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>{$lang_paste_text_desc}</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<script language="javascript" type="text/javascript" src="../../tiny_mce_popup.js"></script>
<script language="javascript" type="text/javascript" src="jscripts/pastetext.js"></script>
<base target="_self" />
</head>
<body onload="tinyMCEPopup.executeOnLoad('onLoadInit();');" onresize="resizeInputs();" style="display: none">
<form name="source" onsubmit="saveContent();">
<div style="float: left" class="title">{$lang_paste_text_desc}</div>
<div style="float: right">
<input type="checkbox" name="linebreaks" id="linebreaks" class="wordWrapCode" checked="checked" /><label for="linebreaks">{$lang_paste_text_linebreaks}</label>
</div>
<br style="clear: both" />
<div>{$lang_paste_text_title}</div>
<textarea name="htmlSource" id="htmlSource" rows="15" cols="100" style="width: 100%; height: 100%; font-family: 'Courier New',Courier,mono; font-size: 12px;" dir="ltr" wrap="soft"></textarea>
<div class="mceActionPanel">
<div style="float: left">
<input type="button" name="insert" value="{$lang_insert}" onclick="saveContent();" id="insert" />
</div>
<div style="float: right">
<input type="button" name="cancel" value="{$lang_cancel}" onclick="tinyMCEPopup.close();" id="cancel" />
</div>
</div>
</form>
</body>
</html>