How to decode javascript error : <p>I am downloading file by clicking on link from ExtJS grid column. </p>

<p>After download When I go back to my Application page I am getting one notification by</p>

<p><strong>The operation failed due to a system error. Please try again.</strong> </p>

<p>In fiddler I am checking</p>

<p>I am getting this error with 200 CODE. </p>

<p>My Question is how to decode this.</p>

<blockquote>
  <p>ErrorInfo=Invalid%20Element%20%22id%22%3A%20%22COSMIC%20Mutation%20Data%20v77%22%3Cbr%3ESource%20%3AExt.dom.Element%3Cbr%3EMethod%3Aconstructor%3Cbr%3E%27
  &amp; ErrSource =Java%20Script</p>
</blockquote>
