Try the following code:
<html>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<xml:namespace prefix="v"/>
<style>
v\:* {behavior=url(#default#VML)}
o\:* {behavior:url(#default#VML);}
</style>
</head>
<body>
<v:background fillcolor="#224452">
<v:fill type="gradient"/>
</v:background>
</body>
</html>
