I am running 5.7 with a theme called Pushbutton.
The them shows up fine in Firefix, but Explorer there is basic
page structure and little else.

Here's a code snippet:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
  <title>Detroiters for Ethics & Accountability in Politics & Education | You elected them.  They work for you.</title>
  <meta http-equiv="Content-Style-Type" content="text/css" />
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css" media="screen, projection, tty, tv, print">
<!--
/* <![CDATA[ */
body {
  font-size: 100% !important;
}
/* ]]>*/
-->
</style>

Thanks.
deape.org