You can try the following code:

 

  <CuteWebUI:Uploader runat="server" ID="Uploader1" InsertText="Upload"
                OnFileUploaded="Uploader_FileUploaded" FileTooLargeMsg="You can customize this msg.{0} cannot be uploaded!
File size ({1}) is too large. The maximum file size allowed is set to: {2}."
                MaxFilesLimitMsg="Please customize msg {0}.">
                <ValidateOption AllowedFileExtensions="jpeg,jpg,gif,png" MaxSizeKB="100" />
            </CuteWebUI:Uploader>

 

Thank you for asking

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