I am developing a page which allows users to select files to upload to my server. While the files are being uploaded, if the user navigates to a different page (using the browser back button, for example) or close the browser, the files will not be uploaded successfully. What would be a usable way to implement a notification?
- Change the upload progress so it opens a modal dialog, showing a progress indicator and an obvious message that the user shouldn't navigate away or close the browser (it wouldn't prevent the user from navigating away or closing the browser, but at least it's obvious something is running)
- Do nothing -- assume most users are aware?