Copy and paste this code and look at the <v:fill tag:
<HTML xmlns:v="urn:schemas-microsoft-com:vml"
xmlns:o="urn:schemas-microsoft-com:office:office">
<HEAD>
<STYLE>
v\:* { behavior: url(#default#VML);}
o\:* { behavior: url(#default#VML);}
</STYLE>
<TITLE>VML Sample</TITLE>
</HEAD>
<BODY bgcolor=#eeeeee>
<v:rect coordsize="21600,21600" style='width:720pt;height:150pt' fillcolor=#446674>
<v:fill method="linear sigma" angle="45" color2="#224452" focus="100%" focusposition=".5,.5" focussize="0,0" type="gradientRadial"/>
<v:shadow on="t" Offset="3pt, 4pt" />
</v:rect>
</body>
</html>