Previously, firefox had the system to automatically resume the failed downloads, but now it's not happening that way.
If the download gets interrupted somehow due to network problems or sleep mode of the laptop, it is not resuming from the same point as it happened before in firefox. Rather, file starts getting downloaded from the beginning.
Opaite Mbohovái (1)
Some websites are set up so that an interrupted download can be resumed. But not all of them.
Go to the Mozilla Add-ons Web Page {web Link} (There’s a lot of good stuff here) and search for a download manager. ++++++++++++++++++++++++++++++++++++++++++ This download manager works separately from the browser. The browser tells it what to download, and off it goes.
http://www.freedownloadmanager.org It is a powerful modern download accelerator and organizer for Windows and Mac.