When I click on "convert" it won't do anything
<pre><code>&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
&lt;head&gt;
&lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8" /&gt;
&lt;title&gt;Untitled Document&lt;/title&gt;
&lt;/head&gt;

&lt;script language="javascript"&gt;


        //This is gobal array for currency and exchange rate which are used in this web page 
        var strCurrency=['Yen','US Dollar','Euro','Swiss Frank','Danish Korona'];
        var dblExchangeRate=[128.7,1.59,1.15,2.06,9.69];

        //this function will allow the user to see if their currency covert
        function Currency()
        {

            //collect information from text boxes and combo box
            var txtSterling=document.getElementById("txtSterling")
            var sleCurrency=document.getElementById("cmbCurrency")
            var txtCovert=document.getElementById("txtCovert")
            var cmbCurrency=document.getElementById("cmbCurrency")

            //this will make sure text box is empty from the start
            txtCovert.value='';

            //this will check to see when the user enter in numbers is vaild and there are no characters
            if (isNaN(txtSterling.value))
            {
                txtSterling.value='';
                alert('Please enter in numerical value only');
                txtSterling.focus();
                return;

                //this will check  the index of cmbCurrency and display the new currency coverstion in txtCovert. This is done by multiplying txtSterling by exchange rate for the new currency 
                var strSlectCurrency= cmbCurrency.selectedIndex;
                var strCurrency= cmbCurrency.options[strSlectCurrency].text;
                txtCovert.value= (txtSterling.value * dblExchangeRate[strSlectCurrency]).toFixed(2) + '' + strCurrency;
            }




        }
&lt;/script&gt;

&lt;body&gt;
&lt;h1 align="center"&gt;Money Currency Converter&lt;/h1&gt;
&lt;p align="left"&gt;&amp;nbsp;&lt;/p&gt;
&lt;p align="left"&gt;Please enter in the amount you wish to covert £ 
  &lt;input type="text" name="txtSterling" id="txtSterling"/&gt;
&lt;/p&gt;
&lt;p align="left"&gt;Please select a currency            
  &lt;select name="cmbCurrency" id="cmbCurrency" onChange="Currency()"&gt;
    &lt;option&gt;Euro&lt;/option&gt;
    &lt;option&gt;US Dollar&lt;/option&gt;
    &lt;option&gt;Swiss Frank&lt;/option&gt;
    &lt;option&gt;Danish Korona&lt;/option&gt;
    &lt;option&gt;Yen&lt;/option&gt;
  &lt;/select&gt;
&lt;/p&gt;
&lt;p align="left"&gt;
  &lt;input type="button" name="cmdCurrency" id="cmdCurrency" value="Convert" onCr65trfg5trrfrfd87lick="Currency()" /&gt;
&lt;/p&gt;
&lt;p align="left"&gt;
  &lt;input type="text" name="txtCovert" id="txtCovert" /&gt;
&lt;/p&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>Why does nothing happen when I click "Convert", despite the fact that I have set an event handler on the button?</p>
