Why does my Public Link give me an Error 404?
It is most likely that the file has not finished uploading to the Dropbox servers. You can check if the file has finished uploading by clicking on the Dropbox icon in your menubar/system tray.
Normally, you will just have to wait a few minutes and try again.
I (AndrewS) wrote a thorough explanation of this here.
Another possible (though more unlikely) reason for this error message is that the Dropbox servers are down. You can check the servers’ status at status.dropbox.com.
And the final possibility is that your link got suspended for using too much bandwidth or because of a DMCA or malware takedown.
And a final even rarer possibility is that you’re unlucky enough to be in one of the few IP-address ranges that Dropbox has blacklisted from hosting .html Public Links (other filetypes still work), because they were being used to host spam/phising/malware.
And if it’s a Public Link to somebody else’s file, maybe they’ve simply renamed/moved/deleted the file in their Dropbox Public folder.