Dropdown related problem

Hi all,

I am new to coldfusion.

I have created a page which has a dropdown and file select button.
After selecting an option from dropdown,
If user selects an invalid file and clicks on upload button I am displaying an error messages like(invalid file,fileformat not proper etc).
Depending on condition i am displaying an error message.
My question is how to hide this message when user changes an option from dropdown.
I dont want to use div.

Please help me out to resolve this issue.

Thanks in advance.