Thank you very much tshering for your help, everything is much clearer now.
Now, I want an image to fill the screen, so I made the following new html page:
<html>
<head>
<title>kobo menu info</title>
<style type="text/css">
p {
margin-top: 0.5em; }
</style>
</head>
<body>
<img src="imgs/Escher_bg.jpg">
</body>
</html>
The image is now displayed in the corner. What I miss is the code to resize the page to fill the screen of my kobo h2o.
Sorry for the very basic question, I would appreciate your help.