[CentOS] firefox keeps downloading .iso files

Whenever I start firfox, it tries to
download two .iso files into Desktop.
Until recently,
I wouldn't notice until it announced that it had run out of room.
At that point I would click on the messages to make them go away.
In the mean time, it had been chewing up bandwidth.

One file, I had tried to download by mistake.
Don't remmeber what I did with it on purpose.
The other I downloaded into a partition with more room.

I found this:
https://support.mozilla.org/en-US/questions/926609
I did not like the side-effects.
For now, I've stopped the downloads by replacing
the target files with empty unreadable files.
Now I get an error message right away and it does not chew up my bandwidth.
I'd lke a better solution.
Any ideas?

[hennebry at localhost firefox]$ uname -a
Linux localhost.localdomain 2.6.32-431.17.1.el6.x86_64 #1 SMP Wed May 7 23:32:49 
UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
[hennebry at localhost firefox]$ firefox --version
Mozilla Firefox 24.5.0
[hennebry at localhost firefox]$

-- 
Michael   hennebry at web.cs.ndsu.NoDak.edu
"SCSI is NOT magic. There are *fundamental technical
reasons* why it is necessary to sacrifice a young
goat to your SCSI chain now and then."   --   John Woods