How to make a textbox to accept only integers as Input.

Html Page:
 <input type="text" name="age" id="txtAge" />&nbsp;<span id="errormsg"></span>

JQuery Snippet for the above TextBox:

Method-1:
$(document).ready(function () {
  //called when key is pressed in textbox
  $("#txtAge").keypress(function (e) {
     //if the letter is not digit then display error and don't type anything
     if (e.which != 8 && e.which != 0 && (e.which < 48 || e.which > 57)) {
        //display error message
        $("#errormsg").html("Digits Only").show().fadeOut("slow");
               return false;
    }
   });
});

Method-2:
$(document).ready(function () {
    $("#txtAge").keydown(function (e) {
        if (e.shiftKey) e.preventDefault();
        else {
            var nKeyCode = e.keyCode;
            //Ignore Backspace (Keycode=8), Tab keys(Keycode=9)  & Delete(Keycode=46)
         if (nKeyCode == 8 || nKeyCode == 9 || nKeyCode == 46) return;
            if (nKeyCode < 95) {
                if (nKeyCode < 48 || nKeyCode > 57) e.preventDefault();
            } else {
                if (nKeyCode < 96 || nKeyCode > 105) e.preventDefault();
            }
        }
    });
});

Enjoy!