<script type="text/javascript">
$(document).ready(function () {
    $(".numberinput").forceNumeric();
});

// forceNumeric() plug-in implementation
jQuery.fn.forceNumeric = function () {
    return this.each(function () {
        $(this).keydown(function (e) {
            var key = e.which || e.keyCode;

            if (!e.shiftKey && !e.altKey && !e.ctrlKey &&
            // numbers
                key >= 48 && key <= 57 ||
            // Numeric keypad
                key >= 96 && key <= 105 ||
            // comma, period and minus, . on keypad
               key == 190 || key == 188 || key == 109 || key == 110 ||
            // Backspace and Tab and Enter
               key == 8 || key == 9 || key == 13 ||
            // Home and End
               key == 35 || key == 36 ||
            // left and right arrows
               key == 37 || key == 39 ||
            // Del and Ins
               key == 46 || key == 45)
                return true;

            return false;
        });
    });
}
</script>
<div class="containercontent">
<div class="label">Enter a number:</div>
<input type="text" name="txtNumber1" id="txtNumber1" value="" class="numberinput" />

<div class="label">Enter a number:</div>
<input type="text" name="txtNumber2" id="txtNumber2" value="" class="numberinput" />
</div>