I have your AjaxUploader running fine using the UploadType=Auto mode in IE and Chrome. However, when I set it to IFrame, it still works in IE, but fails in Chrome. The reason is, our code checks Request validity by checking Request.UrlReferrer to ensure the request is coming from one of our servers. In IE, this works fine, but in Chrome, the Request.UrlReferrer is returning null when trying to upload a file. In all other postbacks, it returns correctly. Any ideas?