Function To Load 2 Frames, For Mulitple Browsers

My problem is that ive made some code for when the user clicks on a button, it will load 2 different pages into 2 separate frames, however it only seems to work when the website is viewed in IE, not firefox or mozilla etc

My two frames are main and main2

The button to return the user to the home page, has the code:
onclick="homeload()"

and i have a javascript function as below in the head of my document:
<script language="JavaScript">
<!--
function homeload() {
parent.document.getElementById("main1").src="home.htm"
parent.document.getElementById("main2").src="home2.htm"
}
// -->
</script>

Any idea how i can make this compatible with mulitple browsers?