Palindrome Game by JavaScript

I just created a very simple game which checks whether a word is a palindrome or not.
You can copy and paste the following code in a html file, then open it in a browser.
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<html>
<head>
    <script type="text/javascript">
    function validatePalindrome()
    {
        if(document.getElementById('palindrome').value.indexOf(' ') != -1)
        {
            alert("Don't enter space");
        }
        else if(document.getElementById('palindrome').value!="")
        {
            var palindrome = document.getElementById('palindrome').value;
            var x=palindrome;
            var w=x.split("");
            var z=x.split("");
            var notpal=1;
            z.reverse();
            for(var i=0; i<w.length; i++)
            {
                if(w[i]!=z[i])
                {
                 alert(palindrome + " is not a palindrome");
                 var notpal=0;
                 break;
                }
            }
            if(notpal==1)
                alert(palindrome + " is a palindrome");
        }
        else
        {
            alert("Enter a word");
        }
    }
    </script>
</head>
<body>
    Please enter a word. The word will be checked if it's palindrome or not.<br />
    <input id="palindrome" type="text" />
    <input onclick="validatePalindrome()" type="button" value="Palindrome" />
</body>
</html>
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 1. Please enter a word

2. Click Palindrome button