General questions

It's a web graphic user interface for the exiftool software (the best tool for manipulating EXIF metadata).
It's linked with Flickr, Dropbox and Google Drive, so you can browse your cloud pictures and edit them directly.
Please take a look at the Supported Files Table and the Medatada Compatibility Table for more informations
I'm sorry no, you can't.
Anyway they'll be deleted automatically after 15 minutes.
Probably because your picture does not contain any EXIF metadata, or just because you've uploaded multiple pictures.
In this case theXifer can't read and combine the EXIF medatada of your pictures, so the form is clean and ready to write your informations into all the uploaded files.

Flickr, Dropbox & Google Drive Questions

Because if you like to edit or update the EXIF information of your Flickr, Dropbox or Google Drive pictures I have to download, edit and replace them.
The "on the fly" editing process available for Flickr, Dropbox or Google Drive is similar to the one of your local files; the eXifer needs to process your pictures, so when you click on the "eXif.me" button located under a Flickr, Dropbox or Google Drive picture this website will download it to read the EXIF recorded metadata, now you can change what you want and by clicking the submit button any changes will be immediately available by replacing the original file.
Absolutely not!
Your pictures will be temporary downloaded just to let you editing them.
The temp files will be deleted as soon as you'll refresh the home page of this site, or automatically after 15 minutes from the download time.
Because this app is able to process only images files - [JPG, TIFF], so all the other files will be ignored.
For example if you have a Dropbox folder with 5 PDF files, 5 ZIP files and 5 JPG files, theXifer will display just 5 jpg images.
Because the Dropbox API does not provide a thumbnail link like the Google Drive or Flickr api, it returns an encoded string with the content of the thumbnail.
theXifer iterate this kind of request to Dropbox one time for each thumbnail, unfortunately this process is really slow, so by default you'll see just a default thumbnail with the Dropbox logo.
Because sometimes the Flickr service slow down and I'm not able to download Thumbs or Picture and let you edit them.
I'm really sorry but I can't control this issue, I can only suggest you to try again later.