Problem
Firefox downloads any file to desktop by default. This soon leads to a cluttered desktop.
The location is not changeable from the download manager, which should have been the obvious place.
Firefox Tools Options

Why
It took me some time to figure out how to change the default download location. So I thought this might me useful to someone else too, who googles for information like me.


Firefox Default Download Location Change
How
Go to Tools menu and click on options as shown.

Then select Downloads from left and change the location as shown.

Click on the images for opening them in a separate page and with full size.

Let me know if this is helpful to you.