Why almost all web site also have this JavaScript?

Hi all,

Why almost all of web site, near the head, also have below code, what is it do for? Why?

<script language=”JavaScript”>
<!–

function SymError()
{
return true;
}

window.onerror = SymError;

var SymRealWinOpen = window.open;

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

window.open = SymWinOpen;

//–>
</script>

Also in #JavaScript _↴