title: why this code has error
body: <pre><code>//this is a part of html code
  &lt;form&gt;
      &lt;b&gt;user:&lt;/b&gt; &lt;input type="text" name="user" size="25"/&gt;
      &lt;input type="button" name ="submit" value="confirm" onclick= "mehdi(this.form)"/&gt;
  &lt;/form&gt;
  &lt;script type="text/javascript"&gt;
      function mehdi(rno){
          rno.user.value =  2 * Math.PI ;//this is error line user is unknown 
  
          alert(rno);
          return rno;
      }
  &lt;/script&gt;
  </code></pre>
  
  <p></p>
  
  <p>what can i do?</p>