i think this code will help you...
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Untitled Document</title>
<script>
function generateRow() {
var d=document.getElementById("div");
d.innerHTML+="<p><input type='text' name='food'>";
}
</script>
</head>
<body>
<form id="form1" name="form1" method="post" action="">
<label>
<input name="food" type="text" id="food" />
</label>
<p>
<input name="food" type="text" id="food" />
</p>
<p>
<input name="food" type="text" id="food" />
</p>
<div id="div"></div>
<p><input type="button" value="Add" onclick="generateRow()"/></p>
<p>
<label>
<input type="submit" name="Submit" value="Submit" />
</label>
</p>
</form>
</body>
</html>