Hide the error message during selected index change event for drop down

Hi

I am having a label to show success message during the successfull save.

I am having a drop down with the name "Technology".

During on selected index change event of the drop down, i am binding another drop down with the name "Resources".

When the Button is clicked, i am showing the "success message"  and on click event of the drop down, i am clearing the message by using the java script.

 function ClearErrorMessage() {

            document.getElementById('ctl00_ContentPlaceHolder1_lblMessage').innerHTML = '';

        }

But when i change the drop down, the message gets reappered.

Can any body help in this issue.

Thanks in advance.