Your paragraph elements have that margin, not the container. So this rule should fix it:
#div_id p {margin: 0;}
Question
If you run the following code you will notice that the word hello is output vertically in a white div with a large distance between each new line. I've tried many different things such as getting rid of the margin style (not sure if it mattered) but no luck finding a solution.
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=windows-1252">
<title>div_experiment</title>
</head>
<body>
<style type = "text/css">
body
{
background-color: black;
}
#div_id
{
position: absolute;
top: 0%;
left: 50%;
margin: 0 auto;
overfill: auto auto;
max-height: 696px;
background-color: white;
font-size: 25px;
}
</style>
<script language="JavaScript">
</script>
<div id = "div_id">
<p>hello</p><br>
<p>hello</p><br>
<p>hello</p><br>
</div>
</body>
</html>
Solution
Your paragraph elements have that margin, not the container. So this rule should fix it:
#div_id p {margin: 0;}