Try to use getElementById() or getElementsByName() to access a specific element and then to use innerHTML property:
<html>
<body>
<div id="myDiv1"></div>
<div id="myDiv2"></div>
</body>
<script type="text/javascript">
var myDiv1 = document.getElementById("myDiv1");
var myDiv2 = document.getElementById("myDiv2");
myDiv1.innerHTML = "<b>Content of 1st DIV</b>";
myDiv2.innerHTML = "<i>Content of second DIV element</i>";
</script>
</html>