[B@rmaley.e><e]

А так?

<script language=javascript>
var pc;
var summa;


function getZakaz(frm)
{
pc=0.05;
if(frm.spnsr.value=='3')
{
pc=0.025;
}
summa=parseInt(frm.summa_o.value);
      pc=summa*pc;
	frm.itogos.value=summa+pc;
}
</script>