If you want to use jQuery then this code can help you...
$(document).ready(function() {
$("#txtboxToFilter").keydown(function (e) {
if ($.inArray(e.keyCode, [46, 8, 9, 27, 13, 110, 190]) !== -1 ||
(e.keyCode == 65 && e.ctrlKey === true) ||
(e.keyCode >= 35 && e.keyCode <= 39)) {
return;
}
if ((e.shiftKey || (e.keyCode < 48 || e.keyCode > 57)) && (e.keyCode < 96 || e.keyCode > 105)) {
e.preventDefault();
}
});
});