document.getElementByID('btnid').disabled is not working in firefox and chrome
===

I am using JavaScript for disabling a button. Works fine in IE but not in FF and chrome, here is the script what iam working on, 

    
    function disbtn(e)   
    { 

        if ( someCondition == true )
          {
              document.getElementById('btn1').disabled = true;
          }
          else
               {
              document.getElementById('btn1').disabled = false;
          }
     

And in my html i have, 

<input type="button" id="btn1" value="submit" />

Any help?
