I created HTML field in SharePoint 2010
<Field ID="{3E83492C-0420-473E-AB65-E4355535AFD0}" Name="MyField" StaticName="MyField" DisplayName="My Field" Type="HTML" Required="FALSE" RichText="TRUE" RichTextMode="FullHtml" >
<Default>
<![CDATA[<div style="background-image:url('http://mytest.com/image.jpg');"><h1>Sample title<h1> <p>sample text</p></div>]]>
</Default>
But when I adding new item to list with this field I don't see background.
When I adding this value manually to field I see image, but if I click Save and open again this field, then this image disappear.
How can I fix this?