<input type="text" onkeypress="return isNumberKey(event,this)">
<script>
function isNumberKey(evt, obj) {
var charCode = (evt.which) ? evt.which : event.keyCode
var value = obj.value;
var dotcontains = value.indexOf(".") != -1;
if (dotcontains)
if (charCode == 46) return false;
if (charCode == 46) return true;
if (charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
}
</script>