Numeric Validation to Accept only numeric values in TextBox using JavaScript

During web development, almost always, we need to provide input validation on even simple web forms. And in case of web, JavaScript is the best option available for validating input on client-side. Server-side validation has its own important and it should be there but restricting user at the very first step is always needed.
 
So, JavaScript functions are explained along with each field for understanding. Let’s take each field one by one with its validation code. 

 Code here:
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
    <style type="text/css">
        body
        {
            font-size: 9pt;
            font-family: Arial;
        }
    </style>
</head>
<body>
    Numeric Value: <input type="text" id="text1" onkeypress="return IsNumeric(event);" ondrop="return false;" onpaste="return false;" />
    <span id="error" style="color: Red; display: none">* Input digits (0 - 9)</span>
    <script type="text/javascript">
        var specialKeys = new Array();
        specialKeys.push(8); //Backspace
        function IsNumeric(e) {
            var keyCode = e.which ? e.which : e.keyCode
            var ret = ((keyCode >= 48 && keyCode <= 57) || specialKeys.indexOf(keyCode) != -1);
            document.getElementById("error").style.display = ret ? "none" : "inline";
            return ret;
        }
    </script>
</body>
</html>