It sounds like it's a browser or a css issue. This code below works and opens the video and puts a div over the bottom right 1/4 of it.
<!DOCTYPE html>
<html>
<head>
<style>
#over
{
display: block;
position: absolute;
left: 240px;
top: 180px;
border: solid 1px black;
width: 480px;
height: 360px;
background-color: white;
z-index: 2;
}
</style>
</head>
<body>
<video style='width: 480px; height: 360px; z-index: 1' src='vid/03.mp4' type='video/mp4'>
Fallback text
</video>
<div id='over'>Some sample content</div>
</body>
</html>