A navbar question about found js code

[chick]

I have not upgraded my boards yet (fear) being long overdue for cleaning them up I noticed in the 'breadcrumbs navbar area' of one, I have found the following JS and do not recall putting it there. Both are 3.6.8 versions. Do I need this JS code on one of boards? when it is not on the other?

<script type="text/javascript">
<!--
function log_out()
{
ht = document.getElementsByTagName("html");
ht[0].style.filter = "progidXImageTransform.Microsoft.BasicImage(gray scale=1)";
if (confirm('$vbphrase[sure_you_want_to_log_out]'))
{
return true;
}
else
{
ht[0].style.filter = "";
return false;
}
}
//-->
</script>
<!-- breadcrumb, login, pm info -->

Thanks for any answer help.