If you want to upload a file that is not one of those, it is best to "zip" the file then upload the ??.zip file.
Here is an example.... I've tried to upload a .xlsx file... no can do.
1. So I zip the .xlsx file to HotCopper.zip.
2. Upload the file to Hotcopper,
3. then a tricky part as there is no clickable link to paste it into the editor box. You need to right click on the ".zip" link found in the upload section below the editor, then click "copy link location". Paste that link into the editor box so other members can get access to the file.
Or
... as the last step, you can also "drag" the name of the file from the upload area into the text area. This hides the full URL of the zip file and makes a slightly cleaner looking post. A user then downloads the .zip file and unzips the .xlsx file.
