1) the style tag in each DIV tag hides each link by default.
2) The togglelink function in the onload event determines which link should be made visible.
<script>
// This script sets OSName variable as follows:
// "Windows" for all versions of Windows
// "MacOS" for all versions of Macintosh OS
// "Linux" for all versions of Linux
// "UNIX" for all other UNIX flavors
// "Unknown OS" indicates failure to detect the OS
var OSName="Unknown OS";
if (navigator.appVersion.indexOf("Win")!=-1) OSName="Windows";
if (navigator.appVersion.indexOf("Mac")!=-1) OSName="MacOS";
if (navigator.appVersion.indexOf("X11")!=-1) OSName="UNIX";
if (navigator.appVersion.indexOf("Linux")!=-1) OSName="Linux";
function togglelink(){
if (OSName=='MacOS'){
//show
document.getElementById("MacLink").style.display='';
//hide
document.getElementById("WindowsLink").style.display='none';
}
else{
//show
document.getElementById("MacLink").style.display='none';
//hide
document.getElementById("WindowsLink").style.display='';
}
}
</script>
<body onload='togglelink();' topmargin="0" leftmargin="0">
<div id="WindowsLink" style="display='none'" align="center">CONTENT HERE</div>
<div id="MacLink" style="display='none'" align="center">CONTENT HERE</div>
</body>