Hi Ardalan,
1. set the mime type like below
<ValidateOption AllowedFileMimeTypes="image/gif,image/jpeg" />
2. The mime type error message is "The file is corrupt or has an incorrect extension. ", you can catch this message link below, then shows your custom error.
<script type="text/javascript">
function CuteWebUI_AjaxUploader_OnError(msg) {
if (msg.indexOf("The file is corrupt or has an incorrect extension") != -1) {
//show the message you want
alert("The file is locked");
return false;
}
}
</script>
Regards,
Ken