[lachild]

According to the documentation you should be able to pass this to the script...

<SCRIPT language="JavaScript">
<!--
if ((screen.width>=1024) && (screen.height>=768))
{
 window.location="home.php?res=high";
}
else
{
  window.location="lowres.html?res=low";
}
//-->
</SCRIPT>

Then what I would do is right above this line in home.php

#
# Assign Smarty variables and show template
#

$smarty->assign("main","catalog");

I might write something like this:

$res = $_GET['res'];

$smarty->assign("res", $res);

Then you should be able to use...

{if $res eq 'high'}
Some Code Here
{else}
Some More code Here
{/if}