HTML Validator plugin FireFox

<script language="JavaScript">
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function SymError()
{
return true;
}

window.onerror = SymError;

var SymRealWinOpen = window.open;

function SymWinOpen(url, name, attributes)
{
return (new Object());
}

window.open = SymWinOpen;

//-->
</script>

<script language="JavaScript">
<!--
var SymRealOnLoad;
var SymRealOnUnload;

function SymOnUnload()
{
window.open = SymWinOpen;
if(SymRealOnUnload != null)
SymRealOnUnload();
}

function SymOnLoad()
{
if(SymRealOnLoad != null)
SymRealOnLoad();
window.open = SymRealWinOpen;
SymRealOnUnload = window.onunload;
window.onunload = SymOnUnload;
}

SymRealOnLoad = window.onload;
window.onload = SymOnLoad;

//-->
</script>

<script type="text/javascript" src="nav.inc.js"></script>